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HybridDictionary Class

Implements IDictionary by using a ListDictionary while the collection is small, and then switching to a Hashtable when the collection gets large.

System.Object
  System.Collections.Specialized.HybridDictionary
    System.Web.Mobile.CookielessData

Namespace:  System.Collections.Specialized
Assembly:  System (in System.dll)
[SerializableAttribute]
public class HybridDictionary : IDictionary, 
	ICollection, IEnumerable

The HybridDictionary type exposes the following members.

  Name Description
Public method Supported by the XNA Framework HybridDictionary Creates an empty case-sensitive HybridDictionary.
Public method Supported by the XNA Framework HybridDictionary(Boolean) Creates an empty HybridDictionary with the specified case sensitivity.
Public method Supported by the XNA Framework HybridDictionary(Int32) Creates a case-sensitive HybridDictionary with the specified initial size.
Public method Supported by the XNA Framework HybridDictionary(Int32, Boolean) Creates a HybridDictionary with the specified initial size and case sensitivity.
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  Name Description
Public property Supported by the XNA Framework Count Gets the number of key/value pairs contained in the HybridDictionary.
Public property Supported by the XNA Framework IsFixedSize Gets a value indicating whether the HybridDictionary has a fixed size.
Public property Supported by the XNA Framework IsReadOnly Gets a value indicating whether the HybridDictionary is read-only.
Public property Supported by the XNA Framework IsSynchronized Gets a value indicating whether the HybridDictionary is synchronized (thread safe).
Public property Supported by the XNA Framework Item Gets or sets the value associated with the specified key.
Public property Supported by the XNA Framework Keys Gets an ICollection containing the keys in the HybridDictionary.
Public property Supported by the XNA Framework SyncRoot Gets an object that can be used to synchronize access to the HybridDictionary.
Public property Supported by the XNA Framework Values Gets an ICollection containing the values in the HybridDictionary.
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  Name Description
Public method Supported by the XNA Framework Add Adds an entry with the specified key and value into the HybridDictionary.
Public method Supported by the XNA Framework Clear Removes all entries from the HybridDictionary.
Public method Supported by the XNA Framework Contains Determines whether the HybridDictionary contains a specific key.
Public method Supported by the XNA Framework CopyTo Copies the HybridDictionary entries to a one-dimensional Array instance at the specified index.
Public method Supported by the XNA Framework Equals(Object) Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected method Supported by the XNA Framework Finalize Allows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public method Supported by the XNA Framework GetEnumerator Returns an IDictionaryEnumerator that iterates through the HybridDictionary.
Public method Supported by the XNA Framework GetHashCode Serves as a hash function for a particular type. (Inherited from Object.)
Public method Supported by the XNA Framework GetType Gets the Type of the current instance. (Inherited from Object.)
Protected method Supported by the XNA Framework MemberwiseClone Creates a shallow copy of the current Object. (Inherited from Object.)
Public method Supported by the XNA Framework Remove Removes the entry with the specified key from the HybridDictionary.
Public method Supported by the XNA Framework ToString Returns a string that represents the current object. (Inherited from Object.)
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  Name Description
Public Extension Method AsParallel Enables parallelization of a query. (Defined by ParallelEnumerable.)
Public Extension Method AsQueryable Converts an IEnumerable to an IQueryable. (Defined by Queryable.)
Public Extension Method Supported by the XNA Framework Cast(Of TResult) Converts the elements of an IEnumerable to the specified type. (Defined by Enumerable.)
Public Extension Method Supported by the XNA Framework OfType(Of TResult) Filters the elements of an IEnumerable based on a specified type. (Defined by Enumerable.)
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  Name Description
Explicit interface implemetation Private method Supported by the XNA Framework IEnumerable.GetEnumerator Returns an IEnumerator that iterates through the HybridDictionary.
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This class is recommended for cases where the number of elements in a dictionary is unknown. It takes advantage of the improved performance of a ListDictionary with small collections, and offers the flexibility of switching to a Hashtable which handles larger collections better than ListDictionary.

If the initial size of the collection is greater than the optimal size for a ListDictionary, the collection is stored in a Hashtable to avoid the overhead of copying elements from the ListDictionary to a Hashtable.

The constructor accepts a Boolean parameter that allows the user to specify whether the collection ignores the case when comparing strings. If the collection is case-sensitive, it uses the key's implementations of Object.GetHashCode and Object.Equals. If the collection is case-insensitive, it performs a simple ordinal case-insensitive comparison, which obeys the casing rules of the invariant culture only. By default, the collection is case-sensitive. For more information on the invariant culture, see System.Globalization.CultureInfo.

A key cannot be null, but a value can.

The foreach statement of the C# language (For Each in Visual Basic) requires the type of each element in the collection. Since each element of the HybridDictionary is a key/value pair, the element type is not the type of the key or the type of the value. Instead, the element type is DictionaryEntry. For example:


foreach (DictionaryEntry de in myHybridDictionary)
{
    //...
}


The foreach statement is a wrapper around the enumerator, which only allows reading from, not writing to, the collection.

The following code example demonstrates several of the properties and methods of HybridDictionary.


using System;
using System.Collections;
using System.Collections.Specialized;

public class SamplesHybridDictionary  {

   public static void Main()  {

      // Creates and initializes a new HybridDictionary.
      HybridDictionary myCol = new HybridDictionary();
      myCol.Add( "Braeburn Apples", "1.49" );
      myCol.Add( "Fuji Apples", "1.29" );
      myCol.Add( "Gala Apples", "1.49" );
      myCol.Add( "Golden Delicious Apples", "1.29" );
      myCol.Add( "Granny Smith Apples", "0.89" );
      myCol.Add( "Red Delicious Apples", "0.99" );
      myCol.Add( "Plantain Bananas", "1.49" );
      myCol.Add( "Yellow Bananas", "0.79" );
      myCol.Add( "Strawberries", "3.33" );
      myCol.Add( "Cranberries", "5.98" );
      myCol.Add( "Navel Oranges", "1.29" );
      myCol.Add( "Grapes", "1.99" );
      myCol.Add( "Honeydew Melon", "0.59" );
      myCol.Add( "Seedless Watermelon", "0.49" );
      myCol.Add( "Pineapple", "1.49" );
      myCol.Add( "Nectarine", "1.99" );
      myCol.Add( "Plums", "1.69" );
      myCol.Add( "Peaches", "1.99" );

      // Display the contents of the collection using foreach. This is the preferred method.
      Console.WriteLine( "Displays the elements using foreach:" );
      PrintKeysAndValues1( myCol );

      // Display the contents of the collection using the enumerator.
      Console.WriteLine( "Displays the elements using the IDictionaryEnumerator:" );
      PrintKeysAndValues2( myCol );

      // Display the contents of the collection using the Keys, Values, Count, and Item properties.
      Console.WriteLine( "Displays the elements using the Keys, Values, Count, and Item properties:" );
      PrintKeysAndValues3( myCol );

      // Copies the HybridDictionary to an array with DictionaryEntry elements.
      DictionaryEntry[] myArr = new DictionaryEntry[myCol.Count];
      myCol.CopyTo( myArr, 0 );

      // Displays the values in the array.
      Console.WriteLine( "Displays the elements in the array:" );
      Console.WriteLine( "   KEY                       VALUE" );
      for ( int i = 0; i < myArr.Length; i++ )
         Console.WriteLine( "   {0,-25} {1}", myArr[i].Key, myArr[i].Value );
      Console.WriteLine();

      // Searches for a key.
      if ( myCol.Contains( "Kiwis" ) )
         Console.WriteLine( "The collection contains the key \"Kiwis\"." );
      else
         Console.WriteLine( "The collection does not contain the key \"Kiwis\"." );
      Console.WriteLine();

      // Deletes a key.
      myCol.Remove( "Plums" );
      Console.WriteLine( "The collection contains the following elements after removing \"Plums\":" );
      PrintKeysAndValues1( myCol );

      // Clears the entire collection.
      myCol.Clear();
      Console.WriteLine( "The collection contains the following elements after it is cleared:" );
      PrintKeysAndValues1( myCol );

   }

   // Uses the foreach statement which hides the complexity of the enumerator.
   // NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
   public static void PrintKeysAndValues1( IDictionary myCol )  {
      Console.WriteLine( "   KEY                       VALUE" );
      foreach ( DictionaryEntry de in myCol )
         Console.WriteLine( "   {0,-25} {1}", de.Key, de.Value );
      Console.WriteLine();
   }

   // Uses the enumerator. 
   // NOTE: The foreach statement is the preferred way of enumerating the contents of a collection.
   public static void PrintKeysAndValues2( IDictionary myCol )  {
      IDictionaryEnumerator myEnumerator = myCol.GetEnumerator();
      Console.WriteLine( "   KEY                       VALUE" );
      while ( myEnumerator.MoveNext() )
         Console.WriteLine( "   {0,-25} {1}", myEnumerator.Key, myEnumerator.Value );
      Console.WriteLine();
   }

   // Uses the Keys, Values, Count, and Item properties.
   public static void PrintKeysAndValues3( HybridDictionary myCol )  {
      String[] myKeys = new String[myCol.Count];
      myCol.Keys.CopyTo( myKeys, 0 );

      Console.WriteLine( "   INDEX KEY                       VALUE" );
      for ( int i = 0; i < myCol.Count; i++ )
         Console.WriteLine( "   {0,-5} {1,-25} {2}", i, myKeys[i], myCol[myKeys[i]] );
      Console.WriteLine();
   }

}

/*
This code produces the following output.

Displays the elements using foreach:
   KEY                       VALUE
   Strawberries              3.33
   Yellow Bananas            0.79
   Cranberries               5.98
   Grapes                    1.99
   Granny Smith Apples       0.89
   Seedless Watermelon       0.49
   Honeydew Melon            0.59
   Red Delicious Apples      0.99
   Navel Oranges             1.29
   Fuji Apples               1.29
   Plantain Bananas          1.49
   Gala Apples               1.49
   Pineapple                 1.49
   Plums                     1.69
   Braeburn Apples           1.49
   Peaches                   1.99
   Golden Delicious Apples   1.29
   Nectarine                 1.99

Displays the elements using the IDictionaryEnumerator:
   KEY                       VALUE
   Strawberries              3.33
   Yellow Bananas            0.79
   Cranberries               5.98
   Grapes                    1.99
   Granny Smith Apples       0.89
   Seedless Watermelon       0.49
   Honeydew Melon            0.59
   Red Delicious Apples      0.99
   Navel Oranges             1.29
   Fuji Apples               1.29
   Plantain Bananas          1.49
   Gala Apples               1.49
   Pineapple                 1.49
   Plums                     1.69
   Braeburn Apples           1.49
   Peaches                   1.99
   Golden Delicious Apples   1.29
   Nectarine                 1.99

Displays the elements using the Keys, Values, Count, and Item properties:
   INDEX KEY                       VALUE
   0     Strawberries              3.33
   1     Yellow Bananas            0.79
   2     Cranberries               5.98
   3     Grapes                    1.99
   4     Granny Smith Apples       0.89
   5     Seedless Watermelon       0.49
   6     Honeydew Melon            0.59
   7     Red Delicious Apples      0.99
   8     Navel Oranges             1.29
   9     Fuji Apples               1.29
   10    Plantain Bananas          1.49
   11    Gala Apples               1.49
   12    Pineapple                 1.49
   13    Plums                     1.69
   14    Braeburn Apples           1.49
   15    Peaches                   1.99
   16    Golden Delicious Apples   1.29
   17    Nectarine                 1.99

Displays the elements in the array:
   KEY                       VALUE
   Strawberries              3.33
   Yellow Bananas            0.79
   Cranberries               5.98
   Grapes                    1.99
   Granny Smith Apples       0.89
   Seedless Watermelon       0.49
   Honeydew Melon            0.59
   Red Delicious Apples      0.99
   Navel Oranges             1.29
   Fuji Apples               1.29
   Plantain Bananas          1.49
   Gala Apples               1.49
   Pineapple                 1.49
   Plums                     1.69
   Braeburn Apples           1.49
   Peaches                   1.99
   Golden Delicious Apples   1.29
   Nectarine                 1.99

The collection does not contain the key "Kiwis".

The collection contains the following elements after removing "Plums":
   KEY                       VALUE
   Strawberries              3.33
   Yellow Bananas            0.79
   Cranberries               5.98
   Grapes                    1.99
   Granny Smith Apples       0.89
   Seedless Watermelon       0.49
   Honeydew Melon            0.59
   Red Delicious Apples      0.99
   Navel Oranges             1.29
   Fuji Apples               1.29
   Plantain Bananas          1.49
   Gala Apples               1.49
   Pineapple                 1.49
   Braeburn Apples           1.49
   Peaches                   1.99
   Golden Delicious Apples   1.29
   Nectarine                 1.99

The collection contains the following elements after it is cleared:
   KEY                       VALUE

*/


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

This implementation does not provide a synchronized (thread safe) wrapper for a HybridDictionary, but derived classes can create their own synchronized versions of the HybridDictionary using the SyncRoot property.

Enumerating through a collection is intrinsically not a thread-safe procedure. Even when a collection is synchronized, other threads can still modify the collection, which causes the enumerator to throw an exception. To guarantee thread safety during enumeration, you can either lock the collection during the entire enumeration or catch the exceptions resulting from changes made by other threads.

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