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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Collections.ObjectModel;
using System.Diagnostics;
namespace Signum.Engine.Linq
{
[DebuggerStepThrough]
public static class ExpressionVisitorHelper
{
public static ReadOnlyCollection<T> NewIfChange<T>( this ReadOnlyCollection<T> collection, Func<T,T> newValue)
where T:class
{
if (collection == null)
return null;
List<T> alternate = null;
for (int i = 0, n = collection.Count; i < n; i++)
{
T item = collection[i];
T newItem = newValue(item);
if (alternate == null && item != newItem)
{
alternate = collection.Take(i).ToList();
}
if (alternate != null && newItem != null)
{
alternate.Add(newItem);
}
}
if (alternate != null)
{
return alternate.AsReadOnly();
}
return collection;
}
public static List<T> NewIfChange<T>(this List<T> collection, Func<T, T> newValue)
where T : class
{
if (collection == null)
return null;
List<T> alternate = null;
for (int i = 0, n = collection.Count; i < n; i++)
{
T item = collection[i];
T newItem = newValue(item);
if (alternate == null && item != newItem)
{
alternate = collection.Take(i).ToList();
}
if (alternate != null && newItem != null)
{
alternate.Add(newItem);
}
}
return alternate ?? collection;
}
}
}
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I'm Computer Scientist, one of the founders of Signum Software, and the lead developer behind Signum Framework.
www.signumframework.com
I love programming in C#, Linq, Compilers, Algorithms, Functional Programming, Computer Graphics, Maths...