c# - HybridDictionary in System.Collections.Specialized

 

As we all know that Dcitinoary provide performance with some sacrifices/overhead on the space, normally the redundancy of space is needed because it has to decrease the amount of contention between different elemetns.

 

 

While HybridDictionary provides a compromise (actually it is not a compromise, it works in that way that if the size of elements is small, then it uses ListDictionary -- we will come to list dictionary later, but if thesize of elements are growing  , then it will  in turns uses HashTable...)

 

 

Let's see the code, 

 

 

public class Class1
  {

    public static void Main(string[] args)
    {

      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 );

    }

    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();
    }


    public static void PrintKeysAndValues2(IDictionary myCol)
    {
      Console.WriteLine("   KEY                 VALUE");
      IDictionaryEnumerator enumerator = myCol.GetEnumerator();
      while (enumerator.MoveNext()) 
      {
        Console.WriteLine("  {0,-25} {1}", enumerator.Key, enumerator.Value);
      }
      Console.WriteLine();
    }

    public static void PrintKeysAndValues3(IDictionary myCol)
    {
      String[] myKeys = new string[myCol.Count];
      myCol.Keys.CopyTo(myKeys, 0); // you can also use the Array.Copy to, but this is much better way to use
      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();

    }
  }

 

 

To bear in mind, you will use the HybridDictionary only when you feel there is a performance bottleneck and the mitigate risk of using a general dictionary for a small set of data or risk of using a ListDictionary for a large set of data. 

 

 

You can find some more information about the use of HybridDictionary at HybridDictionary class