What is HybridDictionary in .Net

HybridDictionary is a specialized Collection in .Net 4. It implements IDictionary by using a ListDictionary when the collection is small, and a Hashtable when the collection is large.

When to Use?

HyBridDictionary 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. 

The foreach statement of 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. 

Example:              

using System;

using System.Collections;

using System.Collections.Specialized; 

public class SamplesHybridDictionary  { 

   public static void Main()  { 

      HybridDictionary myHD = new HybridDictionary ();

      myHD.Add (“ONE", "1”);

      myHD.Add (“TWO", "2”);

      myHD.Add (“THREE", "3”);

      myHD.Add (“FOUR", "4”);      

      Console.WriteLine( "Elements in HybridDictionary Object:” );      

      Console.WriteLine( "   KEY                       VALUE" );

      foreach (DictionaryEntry de in myCol)

         Console.WriteLine (“   {0,-25} {1}", de.Key, de.Value);

      Console.WriteLine ();

}

As it implements the IDictionary, ICollection, IEnumerable interface we can have the Add, Contain, equals etc methods. 

For more information about HybridDictioanry, visit MSDN site

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