Auto-filter for Microsoft WPF DataGrid

//******************************
// Written by Peter Golde
// Copyright (c) 2004-2005, Wintellect
//
// Use and restribution of this code is subject to the license agreement 
// contained in the file "License.txt" accompanying this file.
//******************************

using System;
using System.Collections;
using System.Collections.Generic;

namespace Wintellect.PowerCollections
{
	/// <summary>
	/// OrderedDictionary&lt;TKey, TValue&gt; is a collection that maps keys of type TKey
	/// to values of type TValue. The keys are maintained in a sorted order, and at most one value
	/// is permitted for each key.
	/// </summary>
	/// <remarks>
	/// <p>The keys are compared in one of three ways. If TKey implements IComparable&lt;TKey&gt; or IComparable,
	/// then the CompareTo method of that interface will be used to compare elements. Alternatively, a comparison
	/// function can be passed in either as a delegate, or as an instance of IComparer&lt;TKey&gt;.</p>
	/// <p>OrderedDictionary is implemented as a balanced binary tree. Inserting, deleting, and looking up an
	/// an element all are done in log(N) type, where N is the number of keys in the tree.</p>
	/// <p><see cref="Dictionary&lt;TKey,TValue&gt;"/> is similar, but uses hashing instead of comparison, and does not maintain
	/// the keys in sorted order.</p>
	///</remarks>
	///<seealso cref="Dictionary&lt;TKey,TValue&gt;"/>
    [Serializable]
	public class OrderedDictionary<TKey,TValue>: DictionaryBase<TKey,TValue>, ICloneable
	{
        // The comparer for comparing keys. This is saved to return from the Comparer property,
        // but is otherwise not used.
        private IComparer<TKey> keyComparer;

		// The comparer for comparing key-value pairs.
		private IComparer<KeyValuePair<TKey,TValue>> pairComparer;

		private RedBlackTree<KeyValuePair<TKey,TValue>> tree;

        /// <summary>
        /// Helper function to create a new KeyValuePair struct.
        /// </summary>
        /// <param name="key">The key.</param>
        /// <param name="value">The value.</param>
        /// <returns>A new KeyValuePair.</returns>
        private static KeyValuePair<TKey,TValue> NewPair(TKey key, TValue value) {
            KeyValuePair<TKey, TValue> pair = new KeyValuePair<TKey,TValue>(key,value);
            return pair;
        }

        /// <summary>
        /// Helper function to create a new KeyValuePair struct with a default value.
        /// </summary>
        /// <param name="key">The key.</param>
        /// <returns>A new KeyValuePair.</returns>
        private static KeyValuePair<TKey, TValue> NewPair(TKey key)
        {
            KeyValuePair<TKey, TValue> pair = new KeyValuePair<TKey,TValue>(key, default(TValue));
            return pair;
        }

        /// <summary>
        /// Creates a new OrderedDictionary. The TKey must implemented IComparable&lt;TKey&gt;
		/// or IComparable. 
		/// The CompareTo method of this interface will be used to compare keys in this dictionary.
		/// </summary>
		/// <exception cref="InvalidOperationException">TKey does not implement IComparable&lt;TKey&gt;.</exception>
		public OrderedDictionary() :
            this(Comparers.DefaultComparer<TKey>())
		{
		}

        /// <summary>
        /// Creates a new OrderedDictionary. The Compare method of the passed comparison object
		/// will be used to compare keys in this dictionary.
		/// </summary>
		/// <remarks>
		/// The GetHashCode and Equals methods of the provided IComparer&lt;TKey&gt; will never
		/// be called, and need not be implemented.</remarks>
		/// <param name="comparer">An instance of IComparer&lt;TKey&gt; that will be used to compare keys.</param>
		public OrderedDictionary(IComparer<TKey> comparer) :
            this(null, comparer, Comparers.ComparerKeyValueFromComparerKey<TKey, TValue>(comparer))
		{
            if (comparer == null)
                throw new ArgumentNullException("comparer");
        }

        /// <summary>
		/// Creates a new OrderedDictionary. The passed delegate will be used to compare keys in this dictionary.
		/// </summary>
		/// <param name="comparison">A delegate to a method that will be used to compare keys.</param>
		public OrderedDictionary(Comparison<TKey> comparison) :
            this(null, Comparers.ComparerFromComparison<TKey>(comparison), Comparers.ComparerKeyValueFromComparisonKey<TKey, TValue>(comparison))
		{
        }

        /// <summary>
        /// <para>Creates a new OrderedDictionary. The TKey must implemented IComparable&lt;TKey&gt;
        /// or IComparable. 
        /// The CompareTo method of this interface will be used to compare keys in this dictionary.</para>
        /// <para>A collection and keys and values (typically another dictionary) is used to initialized the 
        /// contents of the dictionary.</para>
        /// </summary>
        /// <param name="keysAndValues">A collection of keys and values whose contents are used to initialized the dictionary.</param>
        /// <exception cref="InvalidOperationException">TKey does not implement IComparable&lt;TKey&gt;.</exception>
        public OrderedDictionary(IEnumerable<KeyValuePair<TKey,TValue>> keysAndValues)
            : this(keysAndValues, Comparers.DefaultComparer<TKey>())
        {
        }

        /// <summary>
        /// <para>Creates a new OrderedDictionary. The Compare method of the passed comparison object
        /// will be used to compare keys in this dictionary.</para>
        /// <para>A collection and keys and values (typically another dictionary) is used to initialized the 
        /// contents of the dictionary.</para>
        /// </summary>
        /// <remarks>
        /// The GetHashCode and Equals methods of the provided IComparer&lt;TKey&gt; will never
        /// be called, and need not be implemented.</remarks>
        /// <param name="keysAndValues">A collection of keys and values whose contents are used to initialized the dictionary.</param>
        /// <param name="comparer">An instance of IComparer&lt;TKey&gt; that will be used to compare keys.</param>
        public OrderedDictionary(IEnumerable<KeyValuePair<TKey, TValue>> keysAndValues, IComparer<TKey> comparer)
            : this(keysAndValues, comparer, Comparers.ComparerKeyValueFromComparerKey<TKey, TValue>(comparer))
        {
            if (comparer == null)
                throw new ArgumentNullException("comparer");
        }

        /// <summary>
        /// <para>Creates a new OrderedDictionary. The passed delegate will be used to compare keys in this dictionary.</para>
        /// <para>A collection and keys and values (typically another dictionary) is used to initialized the 
        /// contents of the dictionary.</para>
        /// </summary>
        /// <param name="keysAndValues">A collection of keys and values whose contents are used to initialized the dictionary.</param>
        /// <param name="comparison">A delegate to a method that will be used to compare keys.</param>
        public OrderedDictionary(IEnumerable<KeyValuePair<TKey, TValue>> keysAndValues, Comparison<TKey> comparison)
            : this(keysAndValues, Comparers.ComparerFromComparison<TKey>(comparison), Comparers.ComparerKeyValueFromComparisonKey<TKey, TValue>(comparison))
        {
        }

        /// <summary>
		/// Creates a new OrderedDictionary. The passed comparer 
		/// will be used to compare key-value pairs in this dictionary. Used internally  
		/// from other constructors.
		/// </summary>
        /// <param name="keysAndValues">A collection of keys and values whose contents are used to initialized the dictionary.</param>
        /// <param name="keyComparer">An IComparer that will be used to compare keys.</param>
        /// <param name="pairComparer">An IComparer that will be used to compare key-value pairs.</param>
        private OrderedDictionary(IEnumerable<KeyValuePair<TKey,TValue>> keysAndValues, IComparer<TKey> keyComparer, IComparer<KeyValuePair<TKey,TValue>> pairComparer)
		{
            this.keyComparer = keyComparer;
            this.pairComparer = pairComparer;
            tree = new RedBlackTree<KeyValuePair<TKey,TValue>>(this.pairComparer);

            if (keysAndValues != null)
                AddMany(keysAndValues);
		}

        /// <summary>
        /// Creates a new OrderedDictionary. The passed comparison delegate 
        /// will be used to compare keys in this dictionary, and the given tree is used. Used internally for Clone().
        /// </summary>
        /// <param name="keyComparer">An IComparer that will be used to compare keys.</param>
        /// <param name="pairComparer">A delegate to a method that will be used to compare key-value pairs.</param>
        /// <param name="tree">RedBlackTree that contains the data for the dictionary.</param>
        private OrderedDictionary(IComparer<TKey> keyComparer, IComparer<KeyValuePair<TKey, TValue>> pairComparer, RedBlackTree<KeyValuePair<TKey, TValue>> tree)
        {
            this.keyComparer = keyComparer;
            this.pairComparer = pairComparer;
            this.tree = tree;
        }

        /// <summary>
        /// Makes a shallow clone of this dictionary; i.e., if keys or values of the
		/// dictionary are reference types, then they are not cloned. If TKey or TValue is a value type,
		/// then each element is copied as if by simple assignment.
		/// </summary>
        /// <remarks>Cloning the dictionary takes time O(N), where N is the number of keys in the dictionary.</remarks>
        /// <returns>The cloned dictionary.</returns>
        public OrderedDictionary<TKey,TValue> Clone()
		{
			OrderedDictionary<TKey,TValue> newDict = new OrderedDictionary<TKey,TValue>(keyComparer, pairComparer, tree.Clone());
			return newDict;
		}

        /// <summary>
        /// Throw an InvalidOperationException indicating that this type is not cloneable.
        /// </summary>
        /// <param name="t">Type to test.</param>
        private void NonCloneableType(Type t)
        {
            throw new InvalidOperationException(string.Format(Strings.TypeNotCloneable, t.FullName));
        }

        /// <summary>
		/// Makes a deep clone of this dictionary. A new dictionary is created with a clone of
		/// each entry of this dictionary, by calling ICloneable.Clone on each element. If TKey or TValue is
		/// a value type, then each element is copied as if by simple assignment.
		/// </summary>
		/// <remarks><para>If TKey or TValue is a reference type, it must implement
        /// ICloneable. Otherwise, an InvalidOperationException is thrown.</para>
        /// <para>Cloning the dictionary takes time O(N log N), where N is the number of keys in the dictionary.</para></remarks>
        /// <returns>The cloned dictionary.</returns>
        /// <exception cref="InvalidOperationException">TKey or TValue is a reference type that does not implement ICloneable.</exception>
		public OrderedDictionary<TKey,TValue> CloneContents()
		{
            bool keyIsValueType, valueIsValueType;

            // Make sure that TKey and TValue can be cloned.
            if (!Util.IsCloneableType(typeof(TKey), out keyIsValueType))
                NonCloneableType(typeof(TKey));

            if (!Util.IsCloneableType(typeof(TValue), out valueIsValueType))
                NonCloneableType(typeof(TValue));

            OrderedDictionary<TKey, TValue> newDict = new OrderedDictionary<TKey, TValue>(null, keyComparer, pairComparer);

            foreach (KeyValuePair<TKey, TValue> pair in tree) {
                // Clone the key and value parts of the pair. Value types can be cloned
                // by just copying them, otherwise, ICloneable is used.
                TKey keyClone;
                TValue valueClone;

                if (keyIsValueType)
                    keyClone = pair.Key;
                else {
                    if (pair.Key == null)
                        keyClone = default(TKey);  // Really null, because we know TKey isn't a value type.
                    else
                        keyClone = (TKey)(((ICloneable)pair.Key).Clone());
                }

                if (valueIsValueType)
                    valueClone = pair.Value;
                else {
                    if (pair.Value == null)
                        valueClone = default(TValue);   // Really null, because we know TKey isn't a value type.
                    else
                        valueClone = (TValue)(((ICloneable)pair.Value).Clone());
                }

                newDict.Add(keyClone, valueClone);
            }

            return newDict;
        }
   
        /// <summary>
        /// Returns the IComparer&lt;T&gt; used to compare keys in this dictionary. 
        /// </summary>
        /// <value>If the dictionary was created using a comparer, that comparer is returned. If the dictionary was
        /// created using a comparison delegate, then a comparer equivalent to that delegate
        /// is returned. Otherwise
        /// the default comparer for TKey (Comparer&lt;TKey&gt;.Default) is returned.</value>
        public IComparer<TKey> Comparer
        {
            get
            {
                return this.keyComparer;
            }
        }


        /// <summary>
        /// Returns a View collection that can be used for enumerating the keys and values in the collection in 
        /// reversed order.
        /// </summary>
        ///<remarks>
        ///<p>Typically, this method is used in conjunction with a foreach statement. For example:
        ///<code>
        /// foreach(KeyValuePair&lt;TKey, TValue&gt; pair in dictionary.Reversed()) {
        ///    // process pair
        /// }
        ///</code></p>
        /// <p>If an entry is added to or deleted from the dictionary while the View is being enumerated, then 
        /// the enumeration will end with an InvalidOperationException.</p>
        ///<p>Calling Reverse does not copy the data in the dictionary, and the operation takes constant time.</p>
        ///</remarks>
        /// <returns>An OrderedDictionary.View of key-value pairs in reverse order.</returns>
        public View Reversed()
        {
            return new View(this, tree.EntireRangeTester, true, true);
        }

        /// <summary>
        /// Returns a collection that can be used for enumerating some of the keys and values in the collection. 
        /// Only keys that are greater than <paramref name="from"/> and 
        /// less than <paramref name="to"/> are included. The keys are enumerated in sorted order.
        /// Keys equal to the end points of the range can be included or excluded depending on the
        /// <paramref name="fromInclusive"/> and <paramref name="toInclusive"/> parameters.
        /// </summary>
        ///<remarks>
        ///<p>If <paramref name="from"/> is greater than or equal to <paramref name="to"/>, the returned collection is empty. </p>
        ///<p>The sorted order of the keys is determined by the comparison instance or delegate used
        /// to create the dictionary.</p>
        ///<p>Typically, this property is used in conjunction with a foreach statement. For example:</p>
        ///<code>
        /// foreach(KeyValuePair&lt;TKey, TValue&gt; pair in dictionary.Range(from, true, to, false)) {
        ///    // process pair
        /// }
        ///</code>
        ///<p>Calling Range does not copy the data in the dictionary, and the operation takes constant time.</p></remarks>
        /// <param name="from">The lower bound of the range.</param>
        /// <param name="fromInclusive">If true, the lower bound is inclusive--keys equal to the lower bound will
        /// be included in the range. If false, the lower bound is exclusive--keys equal to the lower bound will not
        /// be included in the range.</param>
        /// <param name="to">The upper bound of the range. </param>
        /// <param name="toInclusive">If true, the upper bound is inclusive--keys equal to the upper bound will
        /// be included in the range. If false, the upper bound is exclusive--keys equal to the upper bound will not
        /// be included in the range.</param>
        /// <returns>An OrderedDictionary.View of key-value pairs in the given range.</returns>
        public View Range(TKey from, bool fromInclusive, TKey to, bool toInclusive)
        {
            return new View(this, tree.DoubleBoundedRangeTester(NewPair(from), fromInclusive, NewPair(to), toInclusive), false, false);
        }


        /// <summary>
        /// Returns a collection that can be used for enumerating some of the keys and values in the collection. 
        /// Only keys that are greater than (and optionally, equal to) <paramref name="from"/> are included. 
        /// The keys are enumerated in sorted order. Keys equal to <paramref name="from"/> can be included
        /// or excluded depending on the <paramref name="fromInclusive"/> parameter.
        /// </summary>
        ///<remarks>
        ///<p>The sorted order of the keys is determined by the comparison instance or delegate used
        /// to create the dictionary.</p>
        ///<p>Typically, this property is used in conjunction with a foreach statement. For example:</p>
        ///<code>
        /// foreach(KeyValuePair&lt;TKey, TValue&gt; pair in dictionary.RangeFrom(from, true)) {
        ///    // process pair
        /// }
        ///</code>
        ///<p>Calling RangeFrom does not copy of the data in the dictionary, and the operation takes constant time.</p>
        ///</remarks>
        /// <param name="from">The lower bound of the range.</param>
        /// <param name="fromInclusive">If true, the lower bound is inclusive--keys equal to the lower bound will
        /// be included in the range. If false, the lower bound is exclusive--keys equal to the lower bound will not
        /// be included in the range.</param>
        /// <returns>An OrderedDictionary.View of key-value pairs in the given range.</returns>
        public View RangeFrom(TKey from, bool fromInclusive)
        {
            return new View(this, tree.LowerBoundedRangeTester(NewPair(from), fromInclusive), false, false);
        }

        /// <summary>
        /// Returns a collection that can be used for enumerating some of the keys and values in the collection. 
        /// Only items that are less than (and optionally, equal to) <paramref name="to"/> are included. 
        /// The items are enumerated in sorted order. Items equal to <paramref name="to"/> can be included
        /// or excluded depending on the <paramref name="toInclusive"/> parameter.
        /// </summary>
        ///<remarks>
        ///<p>The sorted order of the keys is determined by the comparison instance or delegate used
        /// to create the dictionary.</p>
        ///<p>Typically, this property is used in conjunction with a foreach statement. For example:</p>
        ///<code>
        /// foreach(KeyValuePair&lt;TKey, TValue&gt; pair in dictionary.RangeFrom(from, false)) {
        ///    // process pair
        /// }
        ///</code>
        ///<p>Calling RangeTo does not copy the data in the dictionary, and the operation takes constant time.</p>
        ///</remarks>
        /// <param name="to">The upper bound of the range. </param>
        /// <param name="toInclusive">If true, the upper bound is inclusive--keys equal to the upper bound will
        /// be included in the range. If false, the upper bound is exclusive--keys equal to the upper bound will not
        /// be included in the range.</param>
        /// <returns>An OrderedDictionary.View of key-value pairs in the given range.</returns>
        public View RangeTo(TKey to, bool toInclusive)
        {
            return new View(this, tree.UpperBoundedRangeTester(NewPair(to), toInclusive), false, false);
        }

		#region IDictionary<TKey,TValue> Members

		/// <summary>
		/// Removes the key (and associated value) from the collection that is equal to the passed in key. If
		/// no key in the dictionary is equal to the passed key, false is returned and the 
		/// dictionary is unchanged.
		/// </summary>
		/// <remarks>Equality between keys is determined by the comparison instance or delegate used
		/// to create the dictionary.</remarks>
		/// <param name="key">The key to remove.</param>
		/// <returns>True if the key was found and removed. False if the key was not found.</returns>
        public sealed override bool Remove(TKey key)
        {
            KeyValuePair<TKey, TValue> keyPair = NewPair(key);
			KeyValuePair<TKey, TValue> item;
			return tree.Delete(keyPair, true, out item);
		}

		/// <summary>
		/// Removes all keys and values from the dictionary.
		/// </summary>
        /// <remarks>Clearing the dictionary takes a constant amount of time, regardless of the number of keys in it.</remarks>
        public sealed override void Clear()
        {
            tree.StopEnumerations();  // Invalidate any enumerations.

            // The simplest and fastest way is simply to throw away the old tree and create a new one.
			tree = new RedBlackTree<KeyValuePair<TKey,TValue>>(pairComparer);
		}

        /// <summary>
        /// Finds a key in the dictionary. If the dictionary already contains
        /// a key equal to the passed key, then the existing value is returned via value. If the dictionary
        /// doesn't contain that key, then value is associated with that key.
        /// </summary>
        /// <remarks><para> between keys is determined by the comparison instance or delegate used
        /// to create the dictionary.</para>
        /// <para>This method takes time O(log N), where N is the number of keys in the dictionary. If a value is added, It is more efficient than
        /// calling TryGetValue followed by Add, because the dictionary is not searched twice.</para></remarks>
        /// <param name="key">The new key. </param>
        /// <param name="value">The new value to associated with that key, if the key isn't present. If the key was present, 
        /// returns the exist value associated with that key.</param>
        /// <returns>True if key was already present, false if key wasn't present (and a new value was added).</returns>
        public bool GetValueElseAdd(TKey key, ref TValue value)
        {
            KeyValuePair<TKey, TValue> pair = NewPair(key, value);
            KeyValuePair<TKey, TValue> old;

            bool added = tree.Insert(pair, DuplicatePolicy.DoNothing, out old);
            if (!added) 
                value = old.Value;
            return !added;
        }

        /// <summary>
        /// Adds a new key and value to the dictionary. If the dictionary already contains
        /// a key equal to the passed key, then an ArgumentException is thrown
        /// </summary>
        /// <remarks>
        /// <para>Equality between keys is determined by the comparison instance or delegate used
        /// to create the dictionary.</para>
        /// <para>Adding an key and value takes time O(log N), where N is the number of keys in the dictionary.</para></remarks>
        /// <param name="key">The new key. "null" is a valid key value.</param>
        /// <param name="value">The new value to associated with that key.</param>
        /// <exception cref="ArgumentException">key is already present in the dictionary</exception>
        public sealed override void Add(TKey key, TValue value)
        {
            KeyValuePair<TKey, TValue> pair = NewPair(key, value);
            KeyValuePair<TKey, TValue> dummy;

            bool added = tree.Insert(pair, DuplicatePolicy.DoNothing, out dummy);
            if (! added) 
                throw new ArgumentException(Strings.KeyAlreadyPresent, "key");
        }

        /// <summary>
        /// Changes the value associated with a given key. If the dictionary does not contain
        /// a key equal to the passed key, then an ArgumentException is thrown.
        /// </summary>
        /// <remarks>
        /// <p>Unlike adding or removing an element, changing the value associated with a key
        /// can be performed while an enumeration (foreach) on the the dictionary is in progress.</p>
        /// <p>Equality between keys is determined by the comparison instance or delegate used
        /// to create the dictionary.</p>
        /// <p>Replace takes time O(log N), where N is the number of entries in the dictionary.</p></remarks>
        /// <param name="key">The new key. </param>
        /// <param name="value">The new value to associated with that key.</param>
        /// <exception cref="KeyNotFoundException">key is not present in the dictionary</exception>
        public void Replace(TKey key, TValue value)
        {
            KeyValuePair<TKey, TValue> pair = NewPair(key, value);
            KeyValuePair<TKey, TValue> dummy;

            bool found = tree.Find(pair, true, true, out dummy);
            if (!found)
                throw new KeyNotFoundException(Strings.KeyNotFound);   
        }

        /// <summary>
        /// Adds multiple key-value pairs to a dictionary. If a key exists in both the current instance and dictionaryToAdd,
        /// then the value is updated with the value from <paramref name="keysAndValues>"/> (no exception is thrown).
        /// Since IDictionary&lt;TKey,TValue&gt; inherits from IEnumerable&lt;KeyValuePair&lt;TKey,TValue&gt;&gt;, this
        /// method can be used to merge one dictionary into another.
        /// </summary>
        /// <remarks>AddMany takes time O(M log (N+M)), where M is the size of <paramref name="keysAndValues>"/>, and N is the size of
        /// this dictionary.</remarks>
        /// <param name="keysAndValues">A collection of keys and values whose contents are added to the current dictionary.</param>
        public void AddMany(IEnumerable<KeyValuePair<TKey, TValue>> keysAndValues)
        {
            if (keysAndValues == null)
                throw new ArgumentNullException("keysAndValues");

            foreach (KeyValuePair<TKey, TValue> pair in keysAndValues) {
                this[pair.Key] = pair.Value;
            }
        }

        /// <summary>
        /// Removes all the keys found in another collection (such as an array or List&lt;TKey&gt;). Each key in keyCollectionToRemove
        /// is removed from the dictionary. Keys that are not present are ignored.
        /// </summary>
        /// <remarks>RemoveMany takes time O(M log N), where M is the size of keyCollectionToRemove, and N is this
        /// size of this collection.</remarks>
        /// <returns>The number of keys removed from the dictionary.</returns>
        /// <param name="keyCollectionToRemove">A collection of keys to remove from the dictionary.</param>
        public int RemoveMany(IEnumerable<TKey> keyCollectionToRemove)
        {
            if (keyCollectionToRemove == null)
                throw new ArgumentNullException("keyCollectionToRemove");

            int count = 0;

            foreach (TKey key in keyCollectionToRemove) {
                if (this.Remove(key))
                    ++count;
            }

            return count;
        }

		/// <summary>
		/// Gets or sets the value associated with a given key. When getting a value, if this
		/// key is not found in the collection, then an ArgumentException is thrown. When setting
		/// a value, the value replaces any existing value in the dictionary.
		/// </summary>
        /// <remarks>The indexer takes time O(log N), where N is the number of entries in the dictionary.</remarks>
        /// <value>The value associated with the key</value>
        /// <exception cref="ArgumentException">A value is being retrieved, and the key is not present in the dictionary.</exception>
        /// <exception cref="ArgumentNullException"><paramref name="key"/> is null.</exception>
        public sealed override TValue this[TKey key]
        {
			get
			{
                KeyValuePair<TKey,TValue> pairFound;
				bool found;
				
				found = tree.Find(NewPair(key), false, false, out pairFound);
				if (found)
					return pairFound.Value;
				else
					throw new KeyNotFoundException(Strings.KeyNotFound);
			}
			set
			{
                KeyValuePair<TKey, TValue> dummy;
                tree.Insert(NewPair(key, value),
                                DuplicatePolicy.ReplaceLast, out dummy);
			}
		}

		/// <summary>
		/// Determines if this dictionary contains a key equal to <paramref name="key"/>. The dictionary
		/// is not changed.
		/// </summary>
        /// <remarks>Searching the dictionary for a key takes time O(log N), where N is the number of keys in the dictionary.</remarks>
        /// <param name="key">The key to search for.</param>
        /// <returns>True if the dictionary contains key. False if the dictionary does not contain key.</returns>
        public sealed override bool ContainsKey(TKey key)
        {
            KeyValuePair<TKey, TValue> pairFound;

            return tree.Find(NewPair(key), false, false, out pairFound);
		}

        /// <summary>
        /// Determines if this dictionary contains a key equal to <paramref name="key"/>. If so, the value
        /// associated with that key is returned through the value parameter.
        /// </summary>
        /// <remarks>TryGetValue takes time O(log N), where N is the number of entries in the dictionary.</remarks>
        /// <param name="key">The key to search for.</param>
        /// <param name="value">Returns the value associated with key, if true was returned.</param>
        /// <returns>True if the dictionary contains key. False if the dictionary does not contain key.</returns>
        public sealed override bool TryGetValue(TKey key, out TValue value)
        {
            KeyValuePair<TKey, TValue> pairFound;

            bool found = tree.Find(NewPair(key), false, false, out pairFound);
            value = pairFound.Value;
            return found;
        }

        #endregion

		#region ICollection<KeyValuePair<TKey,TValue>> Members

        /// <summary>
        /// Returns the number of keys in the dictionary.
		/// </summary>
        /// <remarks>The size of the dictionary is returned in constant time..</remarks>
        /// <value>The number of keys in the dictionary.</value>
        public sealed override int Count
		{
			get
			{
				return tree.ElementCount;
			}
		}

#endregion

		#region IEnumerable<KeyValuePair<TKey,TValue>> Members

		/// <summary>
		/// Returns an enumerator that enumerates all the entries in the dictionary. Each entry is 
		/// returned as a KeyValuePair&lt;TKey,TValue&gt;.
		/// The entries are enumerated in the sorted order of the keys.
		/// </summary>
		/// <remarks>
		/// <p>Typically, this method is not called directly. Instead the "foreach" statement is used
		/// to enumerate the elements of the dictionary, which uses this method implicitly.</p>
		/// <p>If an element is added to or deleted from the dictionary while it is being enumerated, then 
		/// the enumeration will end with an InvalidOperationException.</p>
		/// <p>Enumeration all the entries in the dictionary takes time O(N log N), where N is the number
		/// of entries in the dictionary.</p>
		/// </remarks>
		/// <returns>An enumerator for enumerating all the elements in the OrderedDictionary.</returns>		
		public sealed override IEnumerator<KeyValuePair<TKey,TValue>> GetEnumerator()
		{
            return tree.GetEnumerator();
		}

		#endregion

		#region ICloneable Members

		/// <summary>
		/// Implements ICloneable.Clone. Makes a shallow clone of this dictionary; i.e., if keys or values are reference types, then they are not cloned.
		/// </summary>
		/// <returns>The cloned dictionary.</returns>
		object ICloneable.Clone()
		{
            return Clone();	
		}

		#endregion

        /// <summary>
        /// The OrderedDictionary&lt;TKey,TValue&gt;.View class is used to look at a subset of the keys and values
        /// inside an ordered dictionary. It is returned from the Range, RangeTo, RangeFrom, and Reversed methods. 
        /// </summary>
        ///<remarks>
        /// <p>Views are dynamic. If the underlying dictionary changes, the view changes in sync. If a change is made
        /// to the view, the underlying dictionary changes accordingly.</p>
        ///<p>Typically, this class is used in conjunction with a foreach statement to enumerate the keys
        /// and values in a subset of the OrderedDictionary. For example:</p>
        ///<code>
        /// foreach(KeyValuePair&lt;TKey, TValue&gt; pair in dictionary.Range(from, to)) {
        ///    // process pair
        /// }
        ///</code>
        ///</remarks>
        [Serializable]
        public class View : DictionaryBase<TKey, TValue>
        {
            private OrderedDictionary<TKey,TValue> myDictionary;
            private RedBlackTree<KeyValuePair<TKey,TValue>>.RangeTester rangeTester;   // range tester for the range being used.
            private bool entireTree;                   // is the view the whole tree?
            private bool reversed;                     // is the view reversed?

            /// <summary>
            /// Initialize the View.
            /// </summary>
            /// <param name="myDictionary">Associated OrderedDictionary to be viewed.</param>
            /// <param name="rangeTester">Range tester that defines the range being used.</param>
            /// <param name="entireTree">If true, then rangeTester defines the entire tree.</param>
            /// <param name="reversed">Is the view enuemerated in reverse order?</param>
            internal View(OrderedDictionary<TKey, TValue> myDictionary, RedBlackTree<KeyValuePair<TKey, TValue>>.RangeTester rangeTester, bool entireTree, bool reversed)
            {
                this.myDictionary = myDictionary;
                this.rangeTester = rangeTester;
                this.entireTree = entireTree;
                this.reversed = reversed;
            }

            /// <summary>
            /// Determine if the given key lies within the bounds of this view.
            /// </summary>
            /// <param name="key">Key to test.</param>
            /// <returns>True if the key is within the bounds of this view.</returns>
            private bool KeyInView(TKey key)
            {
                return rangeTester(NewPair(key, default(TValue))) == 0;
            }

            /// <summary>
            /// Enumerate all the keys and values in this view.
            /// </summary>
            /// <returns>An IEnumerator of KeyValuePairs with the keys and views in this view.</returns>
            public sealed override IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
            {
                if (reversed)
                    return myDictionary.tree.EnumerateRangeReversed(rangeTester).GetEnumerator();
                else
                    return myDictionary.tree.EnumerateRange(rangeTester).GetEnumerator();
            }

            /// <summary>
            /// Number of keys in this view.
            /// </summary>
            /// <value>Number of keys that lie within the bounds the view.</value>
            public sealed override int Count
            {
                get
                {
                    if (entireTree)
                        return myDictionary.Count;
                    else
                        return myDictionary.tree.CountRange(rangeTester);
                }
            }

            /// <summary>
            /// Tests if the key is present in the part of the dictionary being viewed.
            /// </summary>
            /// <param name="key">Key to check for.</param>
            /// <returns>True if the key is within this view. </returns>
            public sealed override bool ContainsKey(TKey key)
            {
                if (!KeyInView(key))
                    return false;
                else
                    return myDictionary.ContainsKey(key);
            }

            /// <summary>
            /// Determines if this view contains a key equal to <paramref name="key"/>. If so, the value
            /// associated with that key is returned through the value parameter. 
            /// </summary>
            /// <param name="key">The key to search for.</param>
            /// <param name="value">Returns the value associated with key, if true was returned.</param>
            /// <returns>True if the key is within this view. </returns>
            public sealed override bool TryGetValue(TKey key, out TValue value)
            {
                if (!KeyInView(key)) {
                    value = default(TValue);
                    return false;
                }
                else {
                    return myDictionary.TryGetValue(key, out value);
                }
            }

            /// <summary>
            /// Gets or sets the value associated with a given key. When getting a value, if this
            /// key is not found in the collection, then an ArgumentException is thrown. When setting
            /// a value, the value replaces any existing value in the dictionary. When setting a value, the 
            /// key must be within the range of keys being viewed.
            /// </summary>
            /// <value>The value associated with the key.</value>
            /// <exception cref="ArgumentException">A value is being retrieved, and the key is not present in the dictionary, 
            /// or a value is being set, and the key is outside the range of keys being viewed by this View.</exception>
            public sealed override TValue this[TKey key]
            {
                get       // technically we don't need to override this, but fixes a bug in NDOC.
                {
                    return base[key];
                }
                 set
                {
                    if (!KeyInView(key))
                        throw new ArgumentException(Strings.OutOfViewRange, "key");
                    else
                        myDictionary[key] = value;
                }
            }

            /// <summary>
            /// Removes the key (and associated value) from the underlying dictionary of this view. that is equal to the passed in key. If
            /// no key in the view is equal to the passed key, the dictionary and view are unchanged.
            /// </summary>
            /// <param name="key">The key to remove.</param>
            /// <returns>True if the key was found and removed. False if the key was not found.</returns>
            public sealed override bool Remove(TKey key)
            {
                if (!KeyInView(key))
                    return false;
                else
                    return myDictionary.Remove(key);
            }

            /// <summary>
            /// Removes all the keys and values within this view from the underlying OrderedDictionary.
            /// </summary>
            /// <example>The following removes all the keys that start with "A" from an OrderedDictionary.
            /// <code>
            /// dictionary.Range("A", "B").Clear();
            /// </code>
            /// </example>
            public sealed override void Clear()
            {
                if (entireTree) {
                    myDictionary.Clear();
                }
                else {
                    myDictionary.tree.DeleteRange(rangeTester);
                }
            }

            /// <summary>
            /// Creates a new View that has the same keys and values as this, in the reversed order.
            /// </summary>
            /// <returns>A new View that has the reversed order of this view.</returns>
            public View Reversed()
            {
                return new View(myDictionary, rangeTester, entireTree, !reversed);
            }
        }
    }
}