#region License, Terms and Author(s)
//
// LINQBridge
// Copyright (c) 2007-9 Atif Aziz, Joseph Albahari. All rights reserved.
//
// Author(s):
//
// Atif Aziz, http://www.raboof.com
//
// This library is free software; you can redistribute it and/or modify it
// under the terms of the New BSD License, a copy of which should have
// been delivered along with this distribution.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
// PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
#endregion
// $Id: Enumerable.cs 224 2009-10-04 07:13:08Z azizatif $
namespace System.Linq
{
#region Imports
using System;
using System.Collections;
using System.Collections.Generic;
using System.Diagnostics;
using LinqBridge;
#endregion
/// <summary>
/// Provides a set of static (Shared in Visual Basic) methods for
/// querying objects that implement <see cref="IEnumerable{T}" />.
/// </summary>
static partial class Enumerable
{
/// <summary>
/// Returns the input typed as <see cref="IEnumerable{T}"/>.
/// </summary>
public static IEnumerable<TSource> AsEnumerable<TSource>(IEnumerable<TSource> source)
{
return source;
}
/// <summary>
/// Returns an empty <see cref="IEnumerable{T}"/> that has the
/// specified type argument.
/// </summary>
public static IEnumerable<TResult> Empty<TResult>()
{
return Sequence<TResult>.Empty;
}
/// <summary>
/// Converts the elements of an <see cref="IEnumerable"/> to the
/// specified type.
/// </summary>
public static IEnumerable<TResult> Cast<TResult>(
this IEnumerable source)
{
CheckNotNull(source, "source");
return CastYield<TResult>(source);
}
private static IEnumerable<TResult> CastYield<TResult>(
IEnumerable source)
{
foreach (var item in source)
yield return (TResult) item;
}
/// <summary>
/// Filters the elements of an <see cref="IEnumerable"/> based on a specified type.
/// </summary>
public static IEnumerable<TResult> OfType<TResult>(
this IEnumerable source)
{
CheckNotNull(source, "source");
return OfTypeYield<TResult>(source);
}
private static IEnumerable<TResult> OfTypeYield<TResult>(
IEnumerable source)
{
foreach (var item in source)
if (item is TResult)
yield return (TResult) item;
}
/// <summary>
/// Generates a sequence of integral numbers within a specified range.
/// </summary>
/// <param name="start">The value of the first integer in the sequence.</param>
/// <param name="count">The number of sequential integers to generate.</param>
public static IEnumerable<int> Range(int start, int count)
{
if (count < 0)
throw new ArgumentOutOfRangeException("count", count, null);
var end = (long) start + count;
if (end - 1 >= int.MaxValue)
throw new ArgumentOutOfRangeException("count", count, null);
return RangeYield(start, end);
}
private static IEnumerable<int> RangeYield(int start, long end)
{
for (var i = start; i < end; i++)
yield return i;
}
/// <summary>
/// Generates a sequence that contains one repeated value.
/// </summary>
public static IEnumerable<TResult> Repeat<TResult>(TResult element, int count)
{
if (count < 0) throw new ArgumentOutOfRangeException("count", count, null);
return RepeatYield(element, count);
}
private static IEnumerable<TResult> RepeatYield<TResult>(TResult element, int count)
{
for (var i = 0; i < count; i++)
yield return element;
}
/// <summary>
/// Filters a sequence of values based on a predicate.
/// </summary>
public static IEnumerable<TSource> Where<TSource>(
this IEnumerable<TSource> source,
Func<TSource, bool> predicate)
{
CheckNotNull(predicate, "predicate");
return source.Where((item, i) => predicate(item));
}
/// <summary>
/// Filters a sequence of values based on a predicate.
/// Each element's index is used in the logic of the predicate function.
/// </summary>
public static IEnumerable<TSource> Where<TSource>(
this IEnumerable<TSource> source,
Func<TSource, int, bool> predicate)
{
CheckNotNull(source, "source");
CheckNotNull(predicate, "predicate");
return WhereYield(source, predicate);
}
private static IEnumerable<TSource> WhereYield<TSource>(
IEnumerable<TSource> source,
Func<TSource, int, bool> predicate)
{
var i = 0;
foreach (var item in source)
if (predicate(item, i++))
yield return item;
}
/// <summary>
/// Projects each element of a sequence into a new form.
/// </summary>
public static IEnumerable<TResult> Select<TSource, TResult>(
this IEnumerable<TSource> source,
Func<TSource, TResult> selector)
{
CheckNotNull(selector, "selector");
return source.Select((item, i) => selector(item));
}
/// <summary>
/// Projects each element of a sequence into a new form by
/// incorporating the element's index.
/// </summary>
public static IEnumerable<TResult> Select<TSource, TResult>(
this IEnumerable<TSource> source,
Func<TSource, int, TResult> selector)
{
CheckNotNull(source, "source");
CheckNotNull(selector, "selector");
return SelectYield(source, selector);
}
private static IEnumerable<TResult> SelectYield<TSource, TResult>(
IEnumerable<TSource> source,
Func<TSource, int, TResult> selector)
{
var i = 0;
foreach (var item in source)
yield return selector(item, i++);
}
/// <summary>
/// Projects each element of a sequence to an <see cref="IEnumerable{T}" />
/// and flattens the resulting sequences into one sequence.
/// </summary>
public static IEnumerable<TResult> SelectMany<TSource, TResult>(
this IEnumerable<TSource> source,
Func<TSource, IEnumerable<TResult>> selector)
{
CheckNotNull(selector, "selector");
return source.SelectMany((item, i) => selector(item));
}
/// <summary>
/// Projects each element of a sequence to an <see cref="IEnumerable{T}" />,
/// and flattens the resulting sequences into one sequence. The
/// index of each source element is used in the projected form of
/// that element.
/// </summary>
public static IEnumerable<TResult> SelectMany<TSource, TResult>(
this IEnumerable<TSource> source,
Func<TSource, int, IEnumerable<TResult>> selector)
{
CheckNotNull(selector, "selector");
return source.SelectMany(selector, (item, subitem) => subitem);
}
/// <summary>
/// Projects each element of a sequence to an <see cref="IEnumerable{T}" />,
/// flattens the resulting sequences into one sequence, and invokes
/// a result selector function on each element therein.
/// </summary>
public static IEnumerable<TResult> SelectMany<TSource, TCollection, TResult>(
this IEnumerable<TSource> source,
Func<TSource, IEnumerable<TCollection>> collectionSelector,
Func<TSource, TCollection, TResult> resultSelector)
{
CheckNotNull(collectionSelector, "collectionSelector");
return source.SelectMany((item, i) => collectionSelector(item), resultSelector);
}
/// <summary>
/// Projects each element of a sequence to an <see cref="IEnumerable{T}" />,
/// flattens the resulting sequences into one sequence, and invokes
/// a result selector function on each element therein. The index of
/// each source element is used in the intermediate projected form
/// of that element.
/// </summary>
public static IEnumerable<TResult> SelectMany<TSource, TCollection, TResult>(
this IEnumerable<TSource> source,
Func<TSource, int, IEnumerable<TCollection>> collectionSelector,
Func<TSource, TCollection, TResult> resultSelector)
{
CheckNotNull(source, "source");
CheckNotNull(collectionSelector, "collectionSelector");
CheckNotNull(resultSelector, "resultSelector");
return SelectManyYield(source, collectionSelector, resultSelector);
}
private static IEnumerable<TResult> SelectManyYield<TSource, TCollection, TResult>(
this IEnumerable<TSource> source,
Func<TSource, int, IEnumerable<TCollection>> collectionSelector,
Func<TSource, TCollection, TResult> resultSelector)
{
var i = 0;
foreach (var item in source)
foreach (var subitem in collectionSelector(item, i++))
yield return resultSelector(item, subitem);
}
/// <summary>
/// Returns elements from a sequence as long as a specified condition is true.
/// </summary>
public static IEnumerable<TSource> TakeWhile<TSource>(
this IEnumerable<TSource> source,
Func<TSource, bool> predicate)
{
CheckNotNull(predicate, "predicate");
return source.TakeWhile((item, i) => predicate(item));
}
/// <summary>
/// Returns elements from a sequence as long as a specified condition is true.
/// The element's index is used in the logic of the predicate function.
/// </summary>
public static IEnumerable<TSource> TakeWhile<TSource>(
this IEnumerable<TSource> source,
Func<TSource, int, bool> predicate)
{
CheckNotNull(source, "source");
CheckNotNull(predicate, "predicate");
return TakeWhileYield(source, predicate);
}
private static IEnumerable<TSource> TakeWhileYield<TSource>(
this IEnumerable<TSource> source,
Func<TSource, int, bool> predicate)
{
var i = 0;
foreach (var item in source)
if (predicate(item, i++))
yield return item;
else
break;
}
private static class Futures<T>
{
public static readonly Func<T> Default = () => default(T);
public static readonly Func<T> Undefined = () => { throw new InvalidOperationException(); };
}
/// <summary>
/// Base implementation of First operator.
/// </summary>
private static TSource FirstImpl<TSource>(
this IEnumerable<TSource> source,
Func<TSource> empty)
{
CheckNotNull(source, "source");
Debug.Assert(empty != null);
var list = source as IList<TSource>; // optimized case for lists
if (list != null)
return list.Count > 0 ? list[0] : empty();
using (var e = source.GetEnumerator()) // fallback for enumeration
return e.MoveNext() ? e.Current : empty();
}
/// <summary>
/// Returns the first element of a sequence.
/// </summary>
public static TSource First<TSource>(
this IEnumerable<TSource> source)
{
return source.FirstImpl(Futures<TSource>.Undefined);
}
/// <summary>
/// Returns the first element in a sequence that satisfies a specified condition.
/// </summary>
public static TSource First<TSource>(
this IEnumerable<TSource> source,
Func<TSource, bool> predicate)
{
return First(source.Where(predicate));
}
/// <summary>
/// Returns the first element of a sequence, or a default value if
/// the sequence contains no elements.
/// </summary>
public static TSource FirstOrDefault<TSource>(
this IEnumerable<TSource> source)
{
return source.FirstImpl(Futures<TSource>.Default);
}
/// <summary>
/// Returns the first element of the sequence that satisfies a
/// condition or a default value if no such element is found.
/// </summary>
public static TSource FirstOrDefault<TSource>(
this IEnumerable<TSource> source,
Func<TSource, bool> predicate)
{
return FirstOrDefault(source.Where(predicate));
}
/// <summary>
/// Base implementation of Last operator.
/// </summary>
private static TSource LastImpl<TSource>(
this IEnumerable<TSource> source,
Func<TSource> empty)
{
CheckNotNull(source, "source");
var list = source as IList<TSource>; // optimized case for lists
if (list != null)
return list.Count > 0 ? list[list.Count - 1] : empty();
using (var e = source.GetEnumerator())
{
if (!e.MoveNext())
return empty();
var last = e.Current;
while (e.MoveNext())
last = e.Current;
return last;
}
}
/// <summary>
/// Returns the last element of a sequence.
/// </summary>
public static TSource Last<TSource>(
this IEnumerable<TSource> source)
{
return source.LastImpl(Futures<TSource>.Undefined);
}
/// <summary>
/// Returns the last element of a sequence that satisfies a
/// specified condition.
/// </summary>
public static TSource Last<TSource>(
this IEnumerable<TSource> source,
Func<TSource, bool> predicate)
{
return Last(source.Where(predicate));
}
/// <summary>
/// Returns the last element of a sequence, or a default value if
/// the sequence contains no elements.
/// </summary>
public static TSource LastOrDefault<TSource>(
this IEnumerable<TSource> source)
{
return source.LastImpl(Futures<TSource>.Default);
}
/// <summary>
/// Returns the last element of a sequence that satisfies a
/// condition or a default value if no such element is found.
/// </summary>
public static TSource LastOrDefault<TSource>(
this IEnumerable<TSource> source,
Func<TSource, bool> predicate)
{
return LastOrDefault(source.Where(predicate));
}
/// <summary>
/// Base implementation of Single operator.
/// </summary>
private static TSource SingleImpl<TSource>(
this IEnumerable<TSource> source,
Func<TSource> empty)
{
CheckNotNull(source, "source");
using (var e = source.GetEnumerator())
{
if (e.MoveNext())
{
var single = e.Current;
if (!e.MoveNext())
return single;
throw new InvalidOperationException();
}
return empty();
}
}
/// <summary>
/// Returns the only element of a sequence, and throws an exception
/// if there is not exactly one element in the sequence.
/// </summary>
public static TSource Single<TSource>(
this IEnumerable<TSource> source)
{
return source.SingleImpl(Futures<TSource>.Undefined);
}
/// <summary>
/// Returns the only element of a sequence that satisfies a
/// specified condition, and throws an exception if more than one
/// such element exists.
/// </summary>
public static TSource Single<TSource>(
this IEnumerable<TSource> source,
Func<TSource, bool> predicate)
{
return Single(source.Where(predicate));
}
/// <summary>
/// Returns the only element of a sequence, or a default value if
/// the sequence is empty; this method throws an exception if there
/// is more than one element in the sequence.
/// </summary>
public static TSource SingleOrDefault<TSource>(
this IEnumerable<TSource> source)
{
return source.SingleImpl(Futures<TSource>.Default);
}
/// <summary>
/// Returns the only element of a sequence that satisfies a
/// specified condition or a default value if no such element
/// exists; this method throws an exception if more than one element
/// satisfies the condition.
/// </summary>
public static TSource SingleOrDefault<TSource>(
this IEnumerable<TSource> source,
Func<TSource, bool> predicate)
{
return SingleOrDefault(source.Where(predicate));
}
/// <summary>
/// Returns the element at a specified index in a sequence.
/// </summary>
public static TSource ElementAt<TSource>(
this IEnumerable<TSource> source,
int index)
{
CheckNotNull(source, "source");
if (index < 0)
throw new ArgumentOutOfRangeException("index", index, null);
var list = source as IList<TSource>;
if (list != null)
return list[index];
try
{
return source.SkipWhile((item, i) => i < index).First();
}
catch (InvalidOperationException) // if thrown by First
{
throw new ArgumentOutOfRangeException("index", index, null);
}
}
/// <summary>
/// Returns the element at a specified index in a sequence or a
/// default value if the index is out of range.
/// </summary>
public static TSource ElementAtOrDefault<TSource>(
this IEnumerable<TSource> source,
int index)
{
CheckNotNull(source, "source");
if (index < 0)
return default(TSource);
var list = source as IList<TSource>;
if (list != null)
return index < list.Count ? list[index] : default(TSource);
return source.SkipWhile((item, i) => i < index).FirstOrDefault();
}
/// <summary>
/// Inverts the order of the elements in a sequence.
/// </summary>
public static IEnumerable<TSource> Reverse<TSource>(
this IEnumerable<TSource> source)
{
CheckNotNull(source, "source");
return ReverseYield(source);
}
private static IEnumerable<TSource> ReverseYield<TSource>(IEnumerable<TSource> source)
{
var stack = new Stack<TSource>();
foreach (var item in source)
stack.Push(item);
foreach (var item in stack)
yield return item;
}
/// <summary>
/// Returns a specified number of contiguous elements from the start
/// of a sequence.
/// </summary>
public static IEnumerable<TSource> Take<TSource>(
this IEnumerable<TSource> source,
int count)
{
return source.Where((item, i) => i < count);
}
/// <summary>
/// Bypasses a specified number of elements in a sequence and then
/// returns the remaining elements.
/// </summary>
public static IEnumerable<TSource> Skip<TSource>(
this IEnumerable<TSource> source,
int count)
{
return source.Where((item, i) => i >= count);
}
/// <summary>
/// Bypasses elements in a sequence as long as a specified condition
/// is true and then returns the remaining elements.
/// </summary>
public static IEnumerable<TSource> SkipWhile<TSource>(
this IEnumerable<TSource> source,
Func<TSource, bool> predicate)
{
CheckNotNull(predicate, "predicate");
return source.SkipWhile((item, i) => predicate(item));
}
/// <summary>
/// Bypasses elements in a sequence as long as a specified condition
/// is true and then returns the remaining elements. The element's
/// index is used in the logic of the predicate function.
/// </summary>
public static IEnumerable<TSource> SkipWhile<TSource>(
this IEnumerable<TSource> source,
Func<TSource, int, bool> predicate)
{
CheckNotNull(source, "source");
CheckNotNull(predicate, "predicate");
return SkipWhileYield(source, predicate);
}
private static IEnumerable<TSource> SkipWhileYield<TSource>(
IEnumerable<TSource> source,
Func<TSource, int, bool> predicate)
{
using (var e = source.GetEnumerator())
{
for (var i = 0; ; i++)
{
if (!e.MoveNext())
yield break;
if (!predicate(e.Current, i))
break;
}
do { yield return e.Current; } while (e.MoveNext());
}
}
/// <summary>
/// Returns the number of elements in a sequence.
/// </summary>
public static int Count<TSource>(
this IEnumerable<TSource> source)
{
CheckNotNull(source, "source");
var collection = source as ICollection;
return collection != null
? collection.Count
: source.Aggregate(0, (count, item) => checked(count + 1));
}
/// <summary>
/// Returns a number that represents how many elements in the
/// specified sequence satisfy a condition.
/// </summary>
public static int Count<TSource>(
this IEnumerable<TSource> source,
Func<TSource, bool> predicate)
{
return Count(source.Where(predicate));
}
/// <summary>
/// Returns an <see cref="Int64"/> that represents the total number
/// of elements in a sequence.
/// </summary>
public static long LongCount<TSource>(
this IEnumerable<TSource> source)
{
CheckNotNull(source, "source");
var array = source as Array;
return array != null
? array.LongLength
: source.Aggregate(0L, (count, item) => count + 1);
}
/// <summary>
/// Returns an <see cref="Int64"/> that represents how many elements
/// in a sequence satisfy a condition.
/// </summary>
public static long LongCount<TSource>(
this IEnumerable<TSource> source,
Func<TSource, bool> predicate)
{
return LongCount(source.Where(predicate));
}
/// <summary>
/// Concatenates two sequences.
/// </summary>
public static IEnumerable<TSource> Concat<TSource>(
this IEnumerable<TSource> first,
IEnumerable<TSource> second)
{
CheckNotNull(first, "first");
CheckNotNull(second, "second");
return ConcatYield(first, second);
}
private static IEnumerable<TSource> ConcatYield<TSource>(
IEnumerable<TSource> first,
IEnumerable<TSource> second)
{
foreach (var item in first)
yield return item;
foreach (var item in second)
yield return item;
}
/// <summary>
/// Creates a <see cref="List{T}"/> from an <see cref="IEnumerable{T}"/>.
/// </summary>
public static List<TSource> ToList<TSource>(
this IEnumerable<TSource> source)
{
CheckNotNull(source, "source");
return new List<TSource>(source);
}
/// <summary>
/// Creates an array from an <see cref="IEnumerable{T}"/>.
/// </summary>
public static TSource[] ToArray<TSource>(
this IEnumerable<TSource> source)
{
return source.ToList().ToArray();
}
/// <summary>
/// Returns distinct elements from a sequence by using the default
/// equality comparer to compare values.
/// </summary>
public static IEnumerable<TSource> Distinct<TSource>(
this IEnumerable<TSource> source)
{
return Distinct(source, /* comparer */ null);
}
/// <summary>
/// Returns distinct elements from a sequence by using a specified
/// <see cref="IEqualityComparer{T}"/> to compare values.
/// </summary>
public static IEnumerable<TSource> Distinct<TSource>(
this IEnumerable<TSource> source,
IEqualityComparer<TSource> comparer)
{
CheckNotNull(source, "source");
return DistinctYield(source, comparer);
}
private static IEnumerable<TSource> DistinctYield<TSource>(
IEnumerable<TSource> source,
IEqualityComparer<TSource> comparer)
{
var set = new Dictionary<TSource, object>(comparer);
foreach (var item in source)
{
if (set.ContainsKey(item))
continue;
set.Add(item, null);
yield return item;
}
}
/// <summary>
/// Creates a <see cref="Lookup{TKey,TElement}" /> from an
/// <see cref="IEnumerable{T}" /> according to a specified key
/// selector function.
/// </summary>
public static ILookup<TKey, TSource> ToLookup<TSource, TKey>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector)
{
return ToLookup(source, keySelector, e => e, /* comparer */ null);
}
/// <summary>
/// Creates a <see cref="Lookup{TKey,TElement}" /> from an
/// <see cref="IEnumerable{T}" /> according to a specified key
/// selector function and a key comparer.
/// </summary>
public static ILookup<TKey, TSource> ToLookup<TSource, TKey>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector,
IEqualityComparer<TKey> comparer)
{
return ToLookup(source, keySelector, e => e, comparer);
}
/// <summary>
/// Creates a <see cref="Lookup{TKey,TElement}" /> from an
/// <see cref="IEnumerable{T}" /> according to specified key
/// and element selector functions.
/// </summary>
public static ILookup<TKey, TElement> ToLookup<TSource, TKey, TElement>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector,
Func<TSource, TElement> elementSelector)
{
return ToLookup(source, keySelector, elementSelector, /* comparer */ null);
}
/// <summary>
/// Creates a <see cref="Lookup{TKey,TElement}" /> from an
/// <see cref="IEnumerable{T}" /> according to a specified key
/// selector function, a comparer and an element selector function.
/// </summary>
public static ILookup<TKey, TElement> ToLookup<TSource, TKey, TElement>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector,
Func<TSource, TElement> elementSelector,
IEqualityComparer<TKey> comparer)
{
CheckNotNull(source, "source");
CheckNotNull(keySelector, "keySelector");
CheckNotNull(elementSelector, "elementSelector");
var lookup = new Lookup<TKey, TElement>(comparer);
foreach (var item in source)
{
var key = keySelector(item);
var grouping = (Grouping<TKey, TElement>) lookup.Find(key);
if (grouping == null)
{
grouping = new Grouping<TKey, TElement>(key);
lookup.Add(grouping);
}
grouping.Add(elementSelector(item));
}
return lookup;
}
/// <summary>
/// Groups the elements of a sequence according to a specified key
/// selector function.
/// </summary>
public static IEnumerable<IGrouping<TKey, TSource>> GroupBy<TSource, TKey>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector)
{
return GroupBy(source, keySelector, /* comparer */ null);
}
/// <summary>
/// Groups the elements of a sequence according to a specified key
/// selector function and compares the keys by using a specified
/// comparer.
/// </summary>
public static IEnumerable<IGrouping<TKey, TSource>> GroupBy<TSource, TKey>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector,
IEqualityComparer<TKey> comparer)
{
return GroupBy(source, keySelector, e => e, comparer);
}
/// <summary>
/// Groups the elements of a sequence according to a specified key
/// selector function and projects the elements for each group by
/// using a specified function.
/// </summary>
public static IEnumerable<IGrouping<TKey, TElement>> GroupBy<TSource, TKey, TElement>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector,
Func<TSource, TElement> elementSelector)
{
return GroupBy(source, keySelector, elementSelector, /* comparer */ null);
}
/// <summary>
/// Groups the elements of a sequence according to a specified key
/// selector function and creates a result value from each group and
/// its key.
/// </summary>
public static IEnumerable<IGrouping<TKey, TElement>> GroupBy<TSource, TKey, TElement>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector,
Func<TSource, TElement> elementSelector,
IEqualityComparer<TKey> comparer)
{
CheckNotNull(source, "source");
CheckNotNull(keySelector, "keySelector");
CheckNotNull(elementSelector, "elementSelector");
return ToLookup(source, keySelector, elementSelector, comparer);
}
/// <summary>
/// Groups the elements of a sequence according to a key selector
/// function. The keys are compared by using a comparer and each
/// group's elements are projected by using a specified function.
/// </summary>
public static IEnumerable<TResult> GroupBy<TSource, TKey, TResult>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector,
Func<TKey, IEnumerable<TSource>, TResult> resultSelector)
{
return GroupBy(source, keySelector, resultSelector, /* comparer */ null);
}
/// <summary>
/// Groups the elements of a sequence according to a specified key
/// selector function and creates a result value from each group and
/// its key. The elements of each group are projected by using a
/// specified function.
/// </summary>
public static IEnumerable<TResult> GroupBy<TSource, TKey, TResult>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector,
Func<TKey, IEnumerable<TSource>, TResult> resultSelector,
IEqualityComparer<TKey> comparer)
{
CheckNotNull(source, "source");
CheckNotNull(keySelector, "keySelector");
CheckNotNull(resultSelector, "resultSelector");
return ToLookup(source, keySelector, comparer).Select(g => resultSelector(g.Key, g));
}
/// <summary>
/// Groups the elements of a sequence according to a specified key
/// selector function and creates a result value from each group and
/// its key. The keys are compared by using a specified comparer.
/// </summary>
public static IEnumerable<TResult> GroupBy<TSource, TKey, TElement, TResult>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector,
Func<TSource, TElement> elementSelector,
Func<TKey, IEnumerable<TElement>, TResult> resultSelector)
{
return GroupBy(source, keySelector, elementSelector, resultSelector, /* comparer */ null);
}
/// <summary>
/// Groups the elements of a sequence according to a specified key
/// selector function and creates a result value from each group and
/// its key. Key values are compared by using a specified comparer,
/// and the elements of each group are projected by using a
/// specified function.
/// </summary>
public static IEnumerable<TResult> GroupBy<TSource, TKey, TElement, TResult>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector,
Func<TSource, TElement> elementSelector,
Func<TKey, IEnumerable<TElement>, TResult> resultSelector,
IEqualityComparer<TKey> comparer)
{
CheckNotNull(source, "source");
CheckNotNull(keySelector, "keySelector");
CheckNotNull(elementSelector, "elementSelector");
CheckNotNull(resultSelector, "resultSelector");
return ToLookup(source, keySelector, elementSelector, comparer)
.Select(g => resultSelector(g.Key, g));
}
/// <summary>
/// Applies an accumulator function over a sequence.
/// </summary>
public static TSource Aggregate<TSource>(
this IEnumerable<TSource> source,
Func<TSource, TSource, TSource> func)
{
CheckNotNull(source, "source");
CheckNotNull(func, "func");
using (var e = source.GetEnumerator())
{
if (!e.MoveNext())
throw new InvalidOperationException();
return e.Renumerable().Skip(1).Aggregate(e.Current, func);
}
}
/// <summary>
/// Applies an accumulator function over a sequence. The specified
/// seed value is used as the initial accumulator value.
/// </summary>
public static TAccumulate Aggregate<TSource, TAccumulate>(
this IEnumerable<TSource> source,
TAccumulate seed,
Func<TAccumulate, TSource, TAccumulate> func)
{
return Aggregate(source, seed, func, r => r);
}
/// <summary>
/// Applies an accumulator function over a sequence. The specified
/// seed value is used as the initial accumulator value, and the
/// specified function is used to select the result value.
/// </summary>
public static TResult Aggregate<TSource, TAccumulate, TResult>(
this IEnumerable<TSource> source,
TAccumulate seed,
Func<TAccumulate, TSource, TAccumulate> func,
Func<TAccumulate, TResult> resultSelector)
{
CheckNotNull(source, "source");
CheckNotNull(func, "func");
CheckNotNull(resultSelector, "resultSelector");
var result = seed;
foreach (var item in source)
result = func(result, item);
return resultSelector(result);
}
/// <summary>
/// Produces the set union of two sequences by using the default
/// equality comparer.
/// </summary>
public static IEnumerable<TSource> Union<TSource>(
this IEnumerable<TSource> first,
IEnumerable<TSource> second)
{
return Union(first, second, /* comparer */ null);
}
/// <summary>
/// Produces the set union of two sequences by using a specified
/// <see cref="IEqualityComparer{T}" />.
/// </summary>
public static IEnumerable<TSource> Union<TSource>(
this IEnumerable<TSource> first,
IEnumerable<TSource> second,
IEqualityComparer<TSource> comparer)
{
return first.Concat(second).Distinct(comparer);
}
/// <summary>
/// Returns the elements of the specified sequence or the type
/// parameter's default value in a singleton collection if the
/// sequence is empty.
/// </summary>
public static IEnumerable<TSource> DefaultIfEmpty<TSource>(
this IEnumerable<TSource> source)
{
return source.DefaultIfEmpty(default(TSource));
}
/// <summary>
/// Returns the elements of the specified sequence or the specified
/// value in a singleton collection if the sequence is empty.
/// </summary>
public static IEnumerable<TSource> DefaultIfEmpty<TSource>(
this IEnumerable<TSource> source,
TSource defaultValue)
{
CheckNotNull(source, "source");
return DefaultIfEmptyYield(source, defaultValue);
}
private static IEnumerable<TSource> DefaultIfEmptyYield<TSource>(
IEnumerable<TSource> source,
TSource defaultValue)
{
using (var e = source.GetEnumerator())
{
if (!e.MoveNext())
yield return defaultValue;
else
do { yield return e.Current; } while (e.MoveNext());
}
}
/// <summary>
/// Determines whether all elements of a sequence satisfy a condition.
/// </summary>
public static bool All<TSource>(
this IEnumerable<TSource> source,
Func<TSource, bool> predicate)
{
CheckNotNull(source, "source");
CheckNotNull(predicate, "predicate");
foreach (var item in source)
if (!predicate(item))
return false;
return true;
}
/// <summary>
/// Determines whether a sequence contains any elements.
/// </summary>
public static bool Any<TSource>(
this IEnumerable<TSource> source)
{
CheckNotNull(source, "source");
using (var e = source.GetEnumerator())
return e.MoveNext();
}
/// <summary>
/// Determines whether any element of a sequence satisfies a
/// condition.
/// </summary>
public static bool Any<TSource>(
this IEnumerable<TSource> source,
Func<TSource, bool> predicate)
{
return source.Where(predicate).Any();
}
/// <summary>
/// Determines whether a sequence contains a specified element by
/// using the default equality comparer.
/// </summary>
public static bool Contains<TSource>(
this IEnumerable<TSource> source,
TSource value)
{
return source.Contains(value, /* comparer */ null);
}
/// <summary>
/// Determines whether a sequence contains a specified element by
/// using a specified <see cref="IEqualityComparer{T}" />.
/// </summary>
public static bool Contains<TSource>(
this IEnumerable<TSource> source,
TSource value,
IEqualityComparer<TSource> comparer)
{
CheckNotNull(source, "source");
if (comparer == null)
{
var collection = source as ICollection<TSource>;
if (collection != null)
return collection.Contains(value);
}
comparer = comparer ?? EqualityComparer<TSource>.Default;
return source.Any(item => comparer.Equals(item, value));
}
/// <summary>
/// Determines whether two sequences are equal by comparing the
/// elements by using the default equality comparer for their type.
/// </summary>
public static bool SequenceEqual<TSource>(
this IEnumerable<TSource> first,
IEnumerable<TSource> second)
{
return first.SequenceEqual(second, /* comparer */ null);
}
/// <summary>
/// Determines whether two sequences are equal by comparing their
/// elements by using a specified <see cref="IEqualityComparer{T}" />.
/// </summary>
public static bool SequenceEqual<TSource>(
this IEnumerable<TSource> first,
IEnumerable<TSource> second,
IEqualityComparer<TSource> comparer)
{
CheckNotNull(first, "frist");
CheckNotNull(second, "second");
comparer = comparer ?? EqualityComparer<TSource>.Default;
using (IEnumerator<TSource> lhs = first.GetEnumerator(),
rhs = second.GetEnumerator())
{
do
{
if (!lhs.MoveNext())
return !rhs.MoveNext();
if (!rhs.MoveNext())
return false;
}
while (comparer.Equals(lhs.Current, rhs.Current));
}
return false;
}
/// <summary>
/// Base implementation for Min/Max operator.
/// </summary>
private static TSource MinMaxImpl<TSource>(
this IEnumerable<TSource> source,
Func<TSource, TSource, bool> lesser)
{
CheckNotNull(source, "source");
Debug.Assert(lesser != null);
return source.Aggregate((a, item) => lesser(a, item) ? a : item);
}
/// <summary>
/// Base implementation for Min/Max operator for nullable types.
/// </summary>
private static TSource? MinMaxImpl<TSource>(
this IEnumerable<TSource?> source,
TSource? seed, Func<TSource?, TSource?, bool> lesser) where TSource : struct
{
CheckNotNull(source, "source");
Debug.Assert(lesser != null);
return source.Aggregate(seed, (a, item) => lesser(a, item) ? a : item);
// == MinMaxImpl(Repeat<TSource?>(null, 1).Concat(source), lesser);
}
/// <summary>
/// Returns the minimum value in a generic sequence.
/// </summary>
public static TSource Min<TSource>(
this IEnumerable<TSource> source)
{
var comparer = Comparer<TSource>.Default;
return source.MinMaxImpl((x, y) => comparer.Compare(x, y) < 0);
}
/// <summary>
/// Invokes a transform function on each element of a generic
/// sequence and returns the minimum resulting value.
/// </summary>
public static TResult Min<TSource, TResult>(
this IEnumerable<TSource> source,
Func<TSource, TResult> selector)
{
return source.Select(selector).Min();
}
/// <summary>
/// Returns the maximum value in a generic sequence.
/// </summary>
public static TSource Max<TSource>(
this IEnumerable<TSource> source)
{
var comparer = Comparer<TSource>.Default;
return source.MinMaxImpl((x, y) => comparer.Compare(x, y) > 0);
}
/// <summary>
/// Invokes a transform function on each element of a generic
/// sequence and returns the maximum resulting value.
/// </summary>
public static TResult Max<TSource, TResult>(
this IEnumerable<TSource> source,
Func<TSource, TResult> selector)
{
return source.Select(selector).Max();
}
/// <summary>
/// Makes an enumerator seen as enumerable once more.
/// </summary>
/// <remarks>
/// The supplied enumerator must have been started. The first element
/// returned is the element the enumerator was on when passed in.
/// DO NOT use this method if the caller must be a generator. It is
/// mostly safe among aggregate operations.
/// </remarks>
private static IEnumerable<T> Renumerable<T>(this IEnumerator<T> e)
{
Debug.Assert(e != null);
do { yield return e.Current; } while (e.MoveNext());
}
/// <summary>
/// Sorts the elements of a sequence in ascending order according to a key.
/// </summary>
public static IOrderedEnumerable<TSource> OrderBy<TSource, TKey>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector)
{
return source.OrderBy(keySelector, /* comparer */ null);
}
/// <summary>
/// Sorts the elements of a sequence in ascending order by using a
/// specified comparer.
/// </summary>
public static IOrderedEnumerable<TSource> OrderBy<TSource, TKey>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector,
IComparer<TKey> comparer)
{
CheckNotNull(source, "source");
CheckNotNull(keySelector, "keySelector");
return new OrderedEnumerable<TSource, TKey>(source, keySelector, comparer, /* descending */ false);
}
/// <summary>
/// Sorts the elements of a sequence in descending order according to a key.
/// </summary>
public static IOrderedEnumerable<TSource> OrderByDescending<TSource, TKey>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector)
{
return source.OrderByDescending(keySelector, /* comparer */ null);
}
/// <summary>
/// Sorts the elements of a sequence in descending order by using a
/// specified comparer.
/// </summary>
public static IOrderedEnumerable<TSource> OrderByDescending<TSource, TKey>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector,
IComparer<TKey> comparer)
{
CheckNotNull(source, "source");
CheckNotNull(source, "keySelector");
return new OrderedEnumerable<TSource, TKey>(source, keySelector, comparer, /* descending */ true);
}
/// <summary>
/// Performs a subsequent ordering of the elements in a sequence in
/// ascending order according to a key.
/// </summary>
public static IOrderedEnumerable<TSource> ThenBy<TSource, TKey>(
this IOrderedEnumerable<TSource> source,
Func<TSource, TKey> keySelector)
{
return source.ThenBy(keySelector, /* comparer */ null);
}
/// <summary>
/// Performs a subsequent ordering of the elements in a sequence in
/// ascending order by using a specified comparer.
/// </summary>
public static IOrderedEnumerable<TSource> ThenBy<TSource, TKey>(
this IOrderedEnumerable<TSource> source,
Func<TSource, TKey> keySelector,
IComparer<TKey> comparer)
{
CheckNotNull(source, "source");
return source.CreateOrderedEnumerable(keySelector, comparer, /* descending */ false);
}
/// <summary>
/// Performs a subsequent ordering of the elements in a sequence in
/// descending order, according to a key.
/// </summary>
public static IOrderedEnumerable<TSource> ThenByDescending<TSource, TKey>(
this IOrderedEnumerable<TSource> source,
Func<TSource, TKey> keySelector)
{
return source.ThenByDescending(keySelector, /* comparer */ null);
}
/// <summary>
/// Performs a subsequent ordering of the elements in a sequence in
/// descending order by using a specified comparer.
/// </summary>
public static IOrderedEnumerable<TSource> ThenByDescending<TSource, TKey>(
this IOrderedEnumerable<TSource> source,
Func<TSource, TKey> keySelector,
IComparer<TKey> comparer)
{
CheckNotNull(source, "source");
return source.CreateOrderedEnumerable(keySelector, comparer, /* descending */ true);
}
/// <summary>
/// Base implementation for Intersect and Except operators.
/// </summary>
private static IEnumerable<TSource> IntersectExceptImpl<TSource>(
this IEnumerable<TSource> first,
IEnumerable<TSource> second,
IEqualityComparer<TSource> comparer,
bool flag)
{
CheckNotNull(first, "first");
CheckNotNull(second, "second");
var keys = new List<TSource>();
var flags = new Dictionary<TSource, bool>(comparer);
foreach (var item in first.Where(k => !flags.ContainsKey(k)))
{
flags.Add(item, !flag);
keys.Add(item);
}
foreach (var item in second.Where(flags.ContainsKey))
flags[item] = flag;
//
// As per docs, "the marked elements are yielded in the order in
// which they were collected.
//
return keys.Where(item => flags[item]);
}
/// <summary>
/// Produces the set intersection of two sequences by using the
/// default equality comparer to compare values.
/// </summary>
public static IEnumerable<TSource> Intersect<TSource>(
this IEnumerable<TSource> first,
IEnumerable<TSource> second)
{
return first.Intersect(second, /* comparer */ null);
}
/// <summary>
/// Produces the set intersection of two sequences by using the
/// specified <see cref="IEqualityComparer{T}" /> to compare values.
/// </summary>
public static IEnumerable<TSource> Intersect<TSource>(
this IEnumerable<TSource> first,
IEnumerable<TSource> second,
IEqualityComparer<TSource> comparer)
{
return IntersectExceptImpl(first, second, comparer, /* flag */ true);
}
/// <summary>
/// Produces the set difference of two sequences by using the
/// default equality comparer to compare values.
/// </summary>
public static IEnumerable<TSource> Except<TSource>(
this IEnumerable<TSource> first,
IEnumerable<TSource> second)
{
return first.Except(second, /* comparer */ null);
}
/// <summary>
/// Produces the set difference of two sequences by using the
/// specified <see cref="IEqualityComparer{T}" /> to compare values.
/// </summary>
public static IEnumerable<TSource> Except<TSource>(
this IEnumerable<TSource> first,
IEnumerable<TSource> second,
IEqualityComparer<TSource> comparer)
{
return IntersectExceptImpl(first, second, comparer, /* flag */ false);
}
/// <summary>
/// Creates a <see cref="Dictionary{TKey,TValue}" /> from an
/// <see cref="IEnumerable{T}" /> according to a specified key
/// selector function.
/// </summary>
public static Dictionary<TKey, TSource> ToDictionary<TSource, TKey>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector)
{
return source.ToDictionary(keySelector, /* comparer */ null);
}
/// <summary>
/// Creates a <see cref="Dictionary{TKey,TValue}" /> from an
/// <see cref="IEnumerable{T}" /> according to a specified key
/// selector function and key comparer.
/// </summary>
public static Dictionary<TKey, TSource> ToDictionary<TSource, TKey>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector,
IEqualityComparer<TKey> comparer)
{
return source.ToDictionary(keySelector, e => e);
}
/// <summary>
/// Creates a <see cref="Dictionary{TKey,TValue}" /> from an
/// <see cref="IEnumerable{T}" /> according to specified key
/// selector and element selector functions.
/// </summary>
public static Dictionary<TKey, TElement> ToDictionary<TSource, TKey, TElement>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector,
Func<TSource, TElement> elementSelector)
{
return source.ToDictionary(keySelector, elementSelector, /* comparer */ null);
}
/// <summary>
/// Creates a <see cref="Dictionary{TKey,TValue}" /> from an
/// <see cref="IEnumerable{T}" /> according to a specified key
/// selector function, a comparer, and an element selector function.
/// </summary>
public static Dictionary<TKey, TElement> ToDictionary<TSource, TKey, TElement>(
this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector,
Func<TSource, TElement> elementSelector,
IEqualityComparer<TKey> comparer)
{
CheckNotNull(source, "source");
CheckNotNull(keySelector, "keySelector");
CheckNotNull(elementSelector, "elementSelector");
var dict = new Dictionary<TKey, TElement>(comparer);
foreach (var item in source)
{
//
// ToDictionary is meant to throw ArgumentNullException if
// keySelector produces a key that is null and
// Argument exception if keySelector produces duplicate keys
// for two elements. Incidentally, the doucmentation for
// IDictionary<TKey, TValue>.Add says that the Add method
// throws the same exceptions under the same circumstances
// so we don't need to do any additional checking or work
// here and let the Add implementation do all the heavy
// lifting.
//
dict.Add(keySelector(item), elementSelector(item));
}
return dict;
}
/// <summary>
/// Correlates the elements of two sequences based on matching keys.
/// The default equality comparer is used to compare keys.
/// </summary>
public static IEnumerable<TResult> Join<TOuter, TInner, TKey, TResult>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
Func<TOuter, TInner, TResult> resultSelector)
{
return outer.Join(inner, outerKeySelector, innerKeySelector, resultSelector, /* comparer */ null);
}
/// <summary>
/// Correlates the elements of two sequences based on matching keys.
/// The default equality comparer is used to compare keys. A
/// specified <see cref="IEqualityComparer{T}" /> is used to compare keys.
/// </summary>
public static IEnumerable<TResult> Join<TOuter, TInner, TKey, TResult>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
Func<TOuter, TInner, TResult> resultSelector,
IEqualityComparer<TKey> comparer)
{
CheckNotNull(outer, "outer");
CheckNotNull(inner, "inner");
CheckNotNull(outerKeySelector, "outerKeySelector");
CheckNotNull(innerKeySelector, "innerKeySelector");
CheckNotNull(resultSelector, "resultSelector");
var lookup = inner.ToLookup(innerKeySelector, comparer);
return
from o in outer
from i in lookup[outerKeySelector(o)]
select resultSelector(o, i);
}
/// <summary>
/// Correlates the elements of two sequences based on equality of
/// keys and groups the results. The default equality comparer is
/// used to compare keys.
/// </summary>
public static IEnumerable<TResult> GroupJoin<TOuter, TInner, TKey, TResult>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
Func<TOuter, IEnumerable<TInner>, TResult> resultSelector)
{
return outer.GroupJoin(inner, outerKeySelector, innerKeySelector, resultSelector, /* comparer */ null);
}
/// <summary>
/// Correlates the elements of two sequences based on equality of
/// keys and groups the results. The default equality comparer is
/// used to compare keys. A specified <see cref="IEqualityComparer{T}" />
/// is used to compare keys.
/// </summary>
public static IEnumerable<TResult> GroupJoin<TOuter, TInner, TKey, TResult>(
this IEnumerable<TOuter> outer,
IEnumerable<TInner> inner,
Func<TOuter, TKey> outerKeySelector,
Func<TInner, TKey> innerKeySelector,
Func<TOuter, IEnumerable<TInner>, TResult> resultSelector,
IEqualityComparer<TKey> comparer)
{
CheckNotNull(outer, "outer");
CheckNotNull(inner, "inner");
CheckNotNull(outerKeySelector, "outerKeySelector");
CheckNotNull(innerKeySelector, "innerKeySelector");
CheckNotNull(resultSelector, "resultSelector");
var lookup = inner.ToLookup(innerKeySelector, comparer);
return outer.Select(o => resultSelector(o, lookup[outerKeySelector(o)]));
}
[DebuggerStepThrough]
private static void CheckNotNull<T>(T value, string name) where T : class
{
if (value == null)
throw new ArgumentNullException(name);
}
private static class Sequence<T>
{
public static readonly IEnumerable<T> Empty = new T[0];
}
private sealed class Grouping<K, V> : List<V>, IGrouping<K, V>
{
internal Grouping(K key)
{
Key = key;
}
public K Key { get; private set; }
}
}
}
// $Id: Enumerable.g.cs 215 2009-10-03 13:31:49Z azizatif $
namespace System.Linq
{
#region Imports
using System;
using System.Collections.Generic;
#endregion
// This partial implementation was template-generated:
// Sat, 03 Oct 2009 09:42:39 GMT
partial class Enumerable
{
/// <summary>
/// Computes the sum of a sequence of nullable <see cref="System.Int32" /> values.
/// </summary>
public static int Sum(
this IEnumerable<int> source)
{
CheckNotNull(source, "source");
int sum = 0;
foreach (var num in source)
sum = checked(sum + num);
return sum;
}
/// <summary>
/// Computes the sum of a sequence of nullable <see cref="System.Int32" />
/// values that are obtained by invoking a transform function on
/// each element of the input sequence.
/// </summary>
public static int Sum<TSource>(
this IEnumerable<TSource> source,
Func<TSource, int> selector)
{
return source.Select(selector).Sum();
}
/// <summary>
/// Computes the average of a sequence of nullable <see cref="System.Int32" /> values.
/// </summary>
public static double Average(
this IEnumerable<int> source)
{
CheckNotNull(source, "source");
long sum = 0;
long count = 0;
foreach (var num in source)
checked
{
sum += (int) num;
count++;
}
if (count == 0)
throw new InvalidOperationException();
return (double) sum / count;
}
/// <summary>
/// Computes the average of a sequence of nullable <see cref="System.Int32" /> values
/// that are obtained by invoking a transform function on each
/// element of the input sequence.
/// </summary>
public static double Average<TSource>(
this IEnumerable<TSource> source,
Func<TSource, int> selector)
{
return source.Select(selector).Average();
}
/// <summary>
/// Computes the sum of a sequence of <see cref="System.Int32" /> values.
/// </summary>
public static int? Sum(
this IEnumerable<int?> source)
{
CheckNotNull(source, "source");
int sum = 0;
foreach (var num in source)
sum = checked(sum + (num ?? 0));
return sum;
}
/// <summary>
/// Computes the sum of a sequence of <see cref="System.Int32" />
/// values that are obtained by invoking a transform function on
/// each element of the input sequence.
/// </summary>
public static int? Sum<TSource>(
this IEnumerable<TSource> source,
Func<TSource, int?> selector)
{
return source.Select(selector).Sum();
}
/// <summary>
/// Computes the average of a sequence of <see cref="System.Int32" /> values.
/// </summary>
public static double? Average(
this IEnumerable<int?> source)
{
CheckNotNull(source, "source");
long sum = 0;
long count = 0;
foreach (var num in source.Where(n => n != null))
checked
{
sum += (int) num;
count++;
}
if (count == 0)
return null;
return (double?) sum / count;
}
/// <summary>
/// Computes the average of a sequence of <see cref="System.Int32" /> values
/// that are obtained by invoking a transform function on each
/// element of the input sequence.
/// </summary>
public static double? Average<TSource>(
this IEnumerable<TSource> source,
Func<TSource, int?> selector)
{
return source.Select(selector).Average();
}
/// <summary>
/// Returns the minimum value in a sequence of nullable
/// <see cref="System.Int32" /> values.
/// </summary>
public static int? Min(
this IEnumerable<int?> source)
{
CheckNotNull(source, "source");
return MinMaxImpl(source.Where(x => x != null), null, (min, x) => min < x);
}
/// <summary>
/// Invokes a transform function on each element of a sequence and
/// returns the minimum nullable <see cref="System.Int32" /> value.
/// </summary>
public static int? Min<TSource>(
this IEnumerable<TSource> source,
Func<TSource, int?> selector)
{
return source.Select(selector).Min();
}
/// <summary>
/// Returns the maximum value in a sequence of nullable
/// <see cref="System.Int32" /> values.
/// </summary>
public static int? Max(
this IEnumerable<int?> source)
{
CheckNotNull(source, "source");
return MinMaxImpl(source.Where(x => x != null),
null, (max, x) => x == null || (max != null && x.Value < max.Value));
}
/// <summary>
/// Invokes a transform function on each element of a sequence and
/// returns the maximum nullable <see cref="System.Int32" /> value.
/// </summary>
public static int? Max<TSource>(
this IEnumerable<TSource> source,
Func<TSource, int?> selector)
{
return source.Select(selector).Max();
}
/// <summary>
/// Computes the sum of a sequence of nullable <see cref="System.Int64" /> values.
/// </summary>
public static long Sum(
this IEnumerable<long> source)
{
CheckNotNull(source, "source");
long sum = 0;
foreach (var num in source)
sum = checked(sum + num);
return sum;
}
/// <summary>
/// Computes the sum of a sequence of nullable <see cref="System.Int64" />
/// values that are obtained by invoking a transform function on
/// each element of the input sequence.
/// </summary>
public static long Sum<TSource>(
this IEnumerable<TSource> source,
Func<TSource, long> selector)
{
return source.Select(selector).Sum();
}
/// <summary>
/// Computes the average of a sequence of nullable <see cref="System.Int64" /> values.
/// </summary>
public static double Average(
this IEnumerable<long> source)
{
CheckNotNull(source, "source");
long sum = 0;
long count = 0;
foreach (var num in source)
checked
{
sum += (long) num;
count++;
}
if (count == 0)
throw new InvalidOperationException();
return (double) sum / count;
}
/// <summary>
/// Computes the average of a sequence of nullable <see cref="System.Int64" /> values
/// that are obtained by invoking a transform function on each
/// element of the input sequence.
/// </summary>
public static double Average<TSource>(
this IEnumerable<TSource> source,
Func<TSource, long> selector)
{
return source.Select(selector).Average();
}
/// <summary>
/// Computes the sum of a sequence of <see cref="System.Int64" /> values.
/// </summary>
public static long? Sum(
this IEnumerable<long?> source)
{
CheckNotNull(source, "source");
long sum = 0;
foreach (var num in source)
sum = checked(sum + (num ?? 0));
return sum;
}
/// <summary>
/// Computes the sum of a sequence of <see cref="System.Int64" />
/// values that are obtained by invoking a transform function on
/// each element of the input sequence.
/// </summary>
public static long? Sum<TSource>(
this IEnumerable<TSource> source,
Func<TSource, long?> selector)
{
return source.Select(selector).Sum();
}
/// <summary>
/// Computes the average of a sequence of <see cref="System.Int64" /> values.
/// </summary>
public static double? Average(
this IEnumerable<long?> source)
{
CheckNotNull(source, "source");
long sum = 0;
long count = 0;
foreach (var num in source.Where(n => n != null))
checked
{
sum += (long) num;
count++;
}
if (count == 0)
return null;
return (double?) sum / count;
}
/// <summary>
/// Computes the average of a sequence of <see cref="System.Int64" /> values
/// that are obtained by invoking a transform function on each
/// element of the input sequence.
/// </summary>
public static double? Average<TSource>(
this IEnumerable<TSource> source,
Func<TSource, long?> selector)
{
return source.Select(selector).Average();
}
/// <summary>
/// Returns the minimum value in a sequence of nullable
/// <see cref="System.Int64" /> values.
/// </summary>
public static long? Min(
this IEnumerable<long?> source)
{
CheckNotNull(source, "source");
return MinMaxImpl(source.Where(x => x != null), null, (min, x) => min < x);
}
/// <summary>
/// Invokes a transform function on each element of a sequence and
/// returns the minimum nullable <see cref="System.Int64" /> value.
/// </summary>
public static long? Min<TSource>(
this IEnumerable<TSource> source,
Func<TSource, long?> selector)
{
return source.Select(selector).Min();
}
/// <summary>
/// Returns the maximum value in a sequence of nullable
/// <see cref="System.Int64" /> values.
/// </summary>
public static long? Max(
this IEnumerable<long?> source)
{
CheckNotNull(source, "source");
return MinMaxImpl(source.Where(x => x != null),
null, (max, x) => x == null || (max != null && x.Value < max.Value));
}
/// <summary>
/// Invokes a transform function on each element of a sequence and
/// returns the maximum nullable <see cref="System.Int64" /> value.
/// </summary>
public static long? Max<TSource>(
this IEnumerable<TSource> source,
Func<TSource, long?> selector)
{
return source.Select(selector).Max();
}
/// <summary>
/// Computes the sum of a sequence of nullable <see cref="System.Single" /> values.
/// </summary>
public static float Sum(
this IEnumerable<float> source)
{
CheckNotNull(source, "source");
float sum = 0;
foreach (var num in source)
sum = checked(sum + num);
return sum;
}
/// <summary>
/// Computes the sum of a sequence of nullable <see cref="System.Single" />
/// values that are obtained by invoking a transform function on
/// each element of the input sequence.
/// </summary>
public static float Sum<TSource>(
this IEnumerable<TSource> source,
Func<TSource, float> selector)
{
return source.Select(selector).Sum();
}
/// <summary>
/// Computes the average of a sequence of nullable <see cref="System.Single" /> values.
/// </summary>
public static float Average(
this IEnumerable<float> source)
{
CheckNotNull(source, "source");
float sum = 0;
long count = 0;
foreach (var num in source)
checked
{
sum += (float) num;
count++;
}
if (count == 0)
throw new InvalidOperationException();
return (float) sum / count;
}
/// <summary>
/// Computes the average of a sequence of nullable <see cref="System.Single" /> values
/// that are obtained by invoking a transform function on each
/// element of the input sequence.
/// </summary>
public static float Average<TSource>(
this IEnumerable<TSource> source,
Func<TSource, float> selector)
{
return source.Select(selector).Average();
}
/// <summary>
/// Computes the sum of a sequence of <see cref="System.Single" /> values.
/// </summary>
public static float? Sum(
this IEnumerable<float?> source)
{
CheckNotNull(source, "source");
float sum = 0;
foreach (var num in source)
sum = checked(sum + (num ?? 0));
return sum;
}
/// <summary>
/// Computes the sum of a sequence of <see cref="System.Single" />
/// values that are obtained by invoking a transform function on
/// each element of the input sequence.
/// </summary>
public static float? Sum<TSource>(
this IEnumerable<TSource> source,
Func<TSource, float?> selector)
{
return source.Select(selector).Sum();
}
/// <summary>
/// Computes the average of a sequence of <see cref="System.Single" /> values.
/// </summary>
public static float? Average(
this IEnumerable<float?> source)
{
CheckNotNull(source, "source");
float sum = 0;
long count = 0;
foreach (var num in source.Where(n => n != null))
checked
{
sum += (float) num;
count++;
}
if (count == 0)
return null;
return (float?) sum / count;
}
/// <summary>
/// Computes the average of a sequence of <see cref="System.Single" /> values
/// that are obtained by invoking a transform function on each
/// element of the input sequence.
/// </summary>
public static float? Average<TSource>(
this IEnumerable<TSource> source,
Func<TSource, float?> selector)
{
return source.Select(selector).Average();
}
/// <summary>
/// Returns the minimum value in a sequence of nullable
/// <see cref="System.Single" /> values.
/// </summary>
public static float? Min(
this IEnumerable<float?> source)
{
CheckNotNull(source, "source");
return MinMaxImpl(source.Where(x => x != null), null, (min, x) => min < x);
}
/// <summary>
/// Invokes a transform function on each element of a sequence and
/// returns the minimum nullable <see cref="System.Single" /> value.
/// </summary>
public static float? Min<TSource>(
this IEnumerable<TSource> source,
Func<TSource, float?> selector)
{
return source.Select(selector).Min();
}
/// <summary>
/// Returns the maximum value in a sequence of nullable
/// <see cref="System.Single" /> values.
/// </summary>
public static float? Max(
this IEnumerable<float?> source)
{
CheckNotNull(source, "source");
return MinMaxImpl(source.Where(x => x != null),
null, (max, x) => x == null || (max != null && x.Value < max.Value));
}
/// <summary>
/// Invokes a transform function on each element of a sequence and
/// returns the maximum nullable <see cref="System.Single" /> value.
/// </summary>
public static float? Max<TSource>(
this IEnumerable<TSource> source,
Func<TSource, float?> selector)
{
return source.Select(selector).Max();
}
/// <summary>
/// Computes the sum of a sequence of nullable <see cref="System.Double" /> values.
/// </summary>
public static double Sum(
this IEnumerable<double> source)
{
CheckNotNull(source, "source");
double sum = 0;
foreach (var num in source)
sum = checked(sum + num);
return sum;
}
/// <summary>
/// Computes the sum of a sequence of nullable <see cref="System.Double" />
/// values that are obtained by invoking a transform function on
/// each element of the input sequence.
/// </summary>
public static double Sum<TSource>(
this IEnumerable<TSource> source,
Func<TSource, double> selector)
{
return source.Select(selector).Sum();
}
/// <summary>
/// Computes the average of a sequence of nullable <see cref="System.Double" /> values.
/// </summary>
public static double Average(
this IEnumerable<double> source)
{
CheckNotNull(source, "source");
double sum = 0;
long count = 0;
foreach (var num in source)
checked
{
sum += (double) num;
count++;
}
if (count == 0)
throw new InvalidOperationException();
return (double) sum / count;
}
/// <summary>
/// Computes the average of a sequence of nullable <see cref="System.Double" /> values
/// that are obtained by invoking a transform function on each
/// element of the input sequence.
/// </summary>
public static double Average<TSource>(
this IEnumerable<TSource> source,
Func<TSource, double> selector)
{
return source.Select(selector).Average();
}
/// <summary>
/// Computes the sum of a sequence of <see cref="System.Double" /> values.
/// </summary>
public static double? Sum(
this IEnumerable<double?> source)
{
CheckNotNull(source, "source");
double sum = 0;
foreach (var num in source)
sum = checked(sum + (num ?? 0));
return sum;
}
/// <summary>
/// Computes the sum of a sequence of <see cref="System.Double" />
/// values that are obtained by invoking a transform function on
/// each element of the input sequence.
/// </summary>
public static double? Sum<TSource>(
this IEnumerable<TSource> source,
Func<TSource, double?> selector)
{
return source.Select(selector).Sum();
}
/// <summary>
/// Computes the average of a sequence of <see cref="System.Double" /> values.
/// </summary>
public static double? Average(
this IEnumerable<double?> source)
{
CheckNotNull(source, "source");
double sum = 0;
long count = 0;
foreach (var num in source.Where(n => n != null))
checked
{
sum += (double) num;
count++;
}
if (count == 0)
return null;
return (double?) sum / count;
}
/// <summary>
/// Computes the average of a sequence of <see cref="System.Double" /> values
/// that are obtained by invoking a transform function on each
/// element of the input sequence.
/// </summary>
public static double? Average<TSource>(
this IEnumerable<TSource> source,
Func<TSource, double?> selector)
{
return source.Select(selector).Average();
}
/// <summary>
/// Returns the minimum value in a sequence of nullable
/// <see cref="System.Double" /> values.
/// </summary>
public static double? Min(
this IEnumerable<double?> source)
{
CheckNotNull(source, "source");
return MinMaxImpl(source.Where(x => x != null), null, (min, x) => min < x);
}
/// <summary>
/// Invokes a transform function on each element of a sequence and
/// returns the minimum nullable <see cref="System.Double" /> value.
/// </summary>
public static double? Min<TSource>(
this IEnumerable<TSource> source,
Func<TSource, double?> selector)
{
return source.Select(selector).Min();
}
/// <summary>
/// Returns the maximum value in a sequence of nullable
/// <see cref="System.Double" /> values.
/// </summary>
public static double? Max(
this IEnumerable<double?> source)
{
CheckNotNull(source, "source");
return MinMaxImpl(source.Where(x => x != null),
null, (max, x) => x == null || (max != null && x.Value < max.Value));
}
/// <summary>
/// Invokes a transform function on each element of a sequence and
/// returns the maximum nullable <see cref="System.Double" /> value.
/// </summary>
public static double? Max<TSource>(
this IEnumerable<TSource> source,
Func<TSource, double?> selector)
{
return source.Select(selector).Max();
}
/// <summary>
/// Computes the sum of a sequence of nullable <see cref="System.Decimal" /> values.
/// </summary>
public static decimal Sum(
this IEnumerable<decimal> source)
{
CheckNotNull(source, "source");
decimal sum = 0;
foreach (var num in source)
sum = checked(sum + num);
return sum;
}
/// <summary>
/// Computes the sum of a sequence of nullable <see cref="System.Decimal" />
/// values that are obtained by invoking a transform function on
/// each element of the input sequence.
/// </summary>
public static decimal Sum<TSource>(
this IEnumerable<TSource> source,
Func<TSource, decimal> selector)
{
return source.Select(selector).Sum();
}
/// <summary>
/// Computes the average of a sequence of nullable <see cref="System.Decimal" /> values.
/// </summary>
public static decimal Average(
this IEnumerable<decimal> source)
{
CheckNotNull(source, "source");
decimal sum = 0;
long count = 0;
foreach (var num in source)
checked
{
sum += (decimal) num;
count++;
}
if (count == 0)
throw new InvalidOperationException();
return (decimal) sum / count;
}
/// <summary>
/// Computes the average of a sequence of nullable <see cref="System.Decimal" /> values
/// that are obtained by invoking a transform function on each
/// element of the input sequence.
/// </summary>
public static decimal Average<TSource>(
this IEnumerable<TSource> source,
Func<TSource, decimal> selector)
{
return source.Select(selector).Average();
}
/// <summary>
/// Computes the sum of a sequence of <see cref="System.Decimal" /> values.
/// </summary>
public static decimal? Sum(
this IEnumerable<decimal?> source)
{
CheckNotNull(source, "source");
decimal sum = 0;
foreach (var num in source)
sum = checked(sum + (num ?? 0));
return sum;
}
/// <summary>
/// Computes the sum of a sequence of <see cref="System.Decimal" />
/// values that are obtained by invoking a transform function on
/// each element of the input sequence.
/// </summary>
public static decimal? Sum<TSource>(
this IEnumerable<TSource> source,
Func<TSource, decimal?> selector)
{
return source.Select(selector).Sum();
}
/// <summary>
/// Computes the average of a sequence of <see cref="System.Decimal" /> values.
/// </summary>
public static decimal? Average(
this IEnumerable<decimal?> source)
{
CheckNotNull(source, "source");
decimal sum = 0;
long count = 0;
foreach (var num in source.Where(n => n != null))
checked
{
sum += (decimal) num;
count++;
}
if (count == 0)
return null;
return (decimal?) sum / count;
}
/// <summary>
/// Computes the average of a sequence of <see cref="System.Decimal" /> values
/// that are obtained by invoking a transform function on each
/// element of the input sequence.
/// </summary>
public static decimal? Average<TSource>(
this IEnumerable<TSource> source,
Func<TSource, decimal?> selector)
{
return source.Select(selector).Average();
}
/// <summary>
/// Returns the minimum value in a sequence of nullable
/// <see cref="System.Decimal" /> values.
/// </summary>
public static decimal? Min(
this IEnumerable<decimal?> source)
{
CheckNotNull(source, "source");
return MinMaxImpl(source.Where(x => x != null), null, (min, x) => min < x);
}
/// <summary>
/// Invokes a transform function on each element of a sequence and
/// returns the minimum nullable <see cref="System.Decimal" /> value.
/// </summary>
public static decimal? Min<TSource>(
this IEnumerable<TSource> source,
Func<TSource, decimal?> selector)
{
return source.Select(selector).Min();
}
/// <summary>
/// Returns the maximum value in a sequence of nullable
/// <see cref="System.Decimal" /> values.
/// </summary>
public static decimal? Max(
this IEnumerable<decimal?> source)
{
CheckNotNull(source, "source");
return MinMaxImpl(source.Where(x => x != null),
null, (max, x) => x == null || (max != null && x.Value < max.Value));
}
/// <summary>
/// Invokes a transform function on each element of a sequence and
/// returns the maximum nullable <see cref="System.Decimal" /> value.
/// </summary>
public static decimal? Max<TSource>(
this IEnumerable<TSource> source,
Func<TSource, decimal?> selector)
{
return source.Select(selector).Max();
}
}
}
namespace System.Runtime.CompilerServices
{
/// <remarks>
/// This attribute allows us to define extension methods without
/// requiring .NET Framework 3.5. For more information, see the section,
/// <a href="http://msdn.microsoft.com/en-us/magazine/cc163317.aspx#S7">Extension Methods in .NET Framework 2.0 Apps</a>,
/// of <a href="http://msdn.microsoft.com/en-us/magazine/cc163317.aspx">Basic Instincts: Extension Methods</a>
/// column in <a href="http://msdn.microsoft.com/msdnmag/">MSDN Magazine</a>,
/// issue <a href="http://msdn.microsoft.com/en-us/magazine/cc135410.aspx">Nov 2007</a>.
/// </remarks>
[AttributeUsage(AttributeTargets.Method | AttributeTargets.Class | AttributeTargets.Assembly)]
internal sealed class ExtensionAttribute : Attribute { }
}
// $Id: Func.cs 224 2009-10-04 07:13:08Z azizatif $
namespace System
{
#if LINQBRIDGE_LIB
public delegate TResult Func<TResult>();
public delegate TResult Func<T, TResult>(T a);
public delegate TResult Func<T1, T2, TResult>(T1 arg1, T2 arg2);
public delegate TResult Func<T1, T2, T3, TResult>(T1 arg1, T2 arg2, T3 arg3);
public delegate TResult Func<T1, T2, T3, T4, TResult>(T1 arg1, T2 arg2, T3 arg3, T4 arg4);
#else
delegate TResult Func<TResult>();
delegate TResult Func<T, TResult>(T a);
delegate TResult Func<T1, T2, TResult>(T1 arg1, T2 arg2);
delegate TResult Func<T1, T2, T3, TResult>(T1 arg1, T2 arg2, T3 arg3);
delegate TResult Func<T1, T2, T3, T4, TResult>(T1 arg1, T2 arg2, T3 arg3, T4 arg4);
#endif
}
// $Id: IGrouping.cs 225 2009-10-04 07:16:14Z azizatif $
namespace System.Linq
{
#region Imports
using System.Collections.Generic;
#endregion
/// <summary>
/// Represents a collection of objects that have a common key.
/// </summary>
partial interface IGrouping<TKey, TElement> : IEnumerable<TElement>
{
/// <summary>
/// Gets the key of the <see cref="IGrouping{TKey,TElement}" />.
/// </summary>
TKey Key { get; }
}
}
// $Id: ILookup.cs 224 2009-10-04 07:13:08Z azizatif $
namespace System.Linq
{
using System.Collections.Generic;
/// <summary>
/// Defines an indexer, size property, and Boolean search method for
/// data structures that map keys to <see cref="IEnumerable{T}"/>
/// sequences of values.
/// </summary>
partial interface ILookup<TKey, TElement> : IEnumerable<IGrouping<TKey, TElement>>
{
bool Contains(TKey key);
int Count { get; }
IEnumerable<TElement> this[TKey key] { get; }
}
}
// $Id: IOrderedEnumerable.cs 224 2009-10-04 07:13:08Z azizatif $
namespace System.Linq
{
using System.Collections.Generic;
/// <summary>
/// Represents a sorted sequence.
/// </summary>
partial interface IOrderedEnumerable<TElement> : IEnumerable<TElement>
{
/// <summary>
/// Performs a subsequent ordering on the elements of an
/// <see cref="IOrderedEnumerable{T}"/> according to a key.
/// </summary>
IOrderedEnumerable<TElement> CreateOrderedEnumerable<TKey>(
Func<TElement, TKey> keySelector, IComparer<TKey> comparer, bool descending);
}
}
// $Id: Lookup.cs 224 2009-10-04 07:13:08Z azizatif $
namespace System.Linq
{
#region Imports
using System;
using System.Collections;
using System.Collections.Generic;
using IEnumerable=System.Collections.IEnumerable;
#endregion
/// <summary>
/// Represents a collection of keys each mapped to one or more values.
/// </summary>
internal sealed class Lookup<TKey, TElement> : ILookup<TKey, TElement>
{
private readonly Dictionary<TKey, IGrouping<TKey, TElement>> _map;
internal Lookup(IEqualityComparer<TKey> comparer)
{
_map = new Dictionary<TKey, IGrouping<TKey, TElement>>(comparer);
}
internal void Add(IGrouping<TKey, TElement> item)
{
_map.Add(item.Key, item);
}
internal IEnumerable<TElement> Find(TKey key)
{
IGrouping<TKey, TElement> grouping;
return _map.TryGetValue(key, out grouping) ? grouping : null;
}
/// <summary>
/// Gets the number of key/value collection pairs in the <see cref="Lookup{TKey,TElement}" />.
/// </summary>
public int Count
{
get { return _map.Count; }
}
/// <summary>
/// Gets the collection of values indexed by the specified key.
/// </summary>
public IEnumerable<TElement> this[TKey key]
{
get
{
IGrouping<TKey, TElement> result;
return _map.TryGetValue(key, out result) ? result : Enumerable.Empty<TElement>();
}
}
/// <summary>
/// Determines whether a specified key is in the <see cref="Lookup{TKey,TElement}" />.
/// </summary>
public bool Contains(TKey key)
{
return _map.ContainsKey(key);
}
/// <summary>
/// Applies a transform function to each key and its associated
/// values and returns the results.
/// </summary>
public IEnumerable<TResult> ApplyResultSelector<TResult>(
Func<TKey, IEnumerable<TElement>, TResult> resultSelector)
{
if (resultSelector == null)
throw new ArgumentNullException("resultSelector");
foreach (var pair in _map)
yield return resultSelector(pair.Key, pair.Value);
}
/// <summary>
/// Returns a generic enumerator that iterates through the <see cref="Lookup{TKey,TElement}" />.
/// </summary>
public IEnumerator<IGrouping<TKey, TElement>> GetEnumerator()
{
return _map.Values.GetEnumerator();
}
IEnumerator IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
}
}
// $Id: OrderedEnumerable.cs 215 2009-10-03 13:31:49Z azizatif $
namespace LinqBridge
{
#region Imports
using System;
using System.Collections;
using System.Collections.Generic;
using System.Linq;
#endregion
internal sealed class OrderedEnumerable<T, K> : IOrderedEnumerable<T>
{
private readonly IEnumerable<T> _source;
private readonly List<Comparison<T>> _comparisons;
public OrderedEnumerable(IEnumerable<T> source,
Func<T, K> keySelector, IComparer<K> comparer, bool descending) :
this(source, null, keySelector, comparer, descending) {}
private OrderedEnumerable(IEnumerable<T> source, List<Comparison<T>> comparisons,
Func<T, K> keySelector, IComparer<K> comparer, bool descending)
{
if (source == null) throw new ArgumentNullException("source");
if (keySelector == null) throw new ArgumentNullException("keySelector");
_source = source;
comparer = comparer ?? Comparer<K>.Default;
if (comparisons == null)
comparisons = new List<Comparison<T>>(/* capacity */ 4);
comparisons.Add((x, y)
=> (descending ? -1 : 1) * comparer.Compare(keySelector(x), keySelector(y)));
_comparisons = comparisons;
}
public IOrderedEnumerable<T> CreateOrderedEnumerable<KK>(
Func<T, KK> keySelector, IComparer<KK> comparer, bool descending)
{
return new OrderedEnumerable<T, KK>(_source, _comparisons, keySelector, comparer, descending);
}
public IEnumerator<T> GetEnumerator()
{
//
// We sort using List<T>.Sort, but docs say that it performs an
// unstable sort. LINQ, on the other hand, says OrderBy performs
// a stable sort. So convert the source sequence into a sequence
// of tuples where the second element tags the position of the
// element from the source sequence (First). The position is
// then used as a tie breaker when all keys compare equal,
// thus making the sort stable.
//
var list = _source.Select((e, i) => new Tuple<T, int>(e, i)).ToList();
list.Sort((x, y) =>
{
//
// Compare keys from left to right.
//
var comparisons = _comparisons;
for (var i = 0; i < comparisons.Count; i++)
{
var result = comparisons[i](x.First, y.First);
if (result != 0)
return result;
}
//
// All keys compared equal so now break the tie by their
// position in the original sequence, making the sort stable.
//
return x.Second.CompareTo(y.Second);
});
return list.Select(pv => pv.First).GetEnumerator();
}
IEnumerator IEnumerable.GetEnumerator()
{
return GetEnumerator();
}
}
}
// $Id: Tuple.cs 215 2009-10-03 13:31:49Z azizatif $
namespace LinqBridge
{
#region Imports
using System;
using System.Collections.Generic;
using System.Text;
#endregion
[ Serializable ]
internal struct Tuple<TFirst, TSecond> : IEquatable<Tuple<TFirst, TSecond>>
{
public TFirst First { get; private set; }
public TSecond Second { get; private set; }
public Tuple(TFirst first, TSecond second) : this()
{
First = first;
Second = second;
}
public override bool Equals(object obj)
{
return obj != null
&& obj is Tuple<TFirst, TSecond>
&& base.Equals((Tuple<TFirst, TSecond>) obj);
}
public bool Equals(Tuple<TFirst, TSecond> other)
{
return EqualityComparer<TFirst>.Default.Equals(other.First, First)
&& EqualityComparer<TSecond>.Default.Equals(other.Second, Second);
}
public override int GetHashCode()
{
var num = 0x7a2f0b42;
num = (-1521134295 * num) + EqualityComparer<TFirst>.Default.GetHashCode(First);
return (-1521134295 * num) + EqualityComparer<TSecond>.Default.GetHashCode(Second);
}
public override string ToString()
{
return string.Format(@"{{ First = {0}, Second = {1} }}", First, Second);
}
}
}
Submit an article or tip