Creating a HybridDictionary with specified initial size in C#

The HybridDictionary class in C# is a special collection that automatically switches between a ListDictionary for small collections and a Hashtable for larger ones. When creating a HybridDictionary with a specified initial size, you can optimize performance by indicating the expected number of elements.

The HybridDictionary uses a ListDictionary when the collection is small (typically less than 10 items) and switches to a Hashtable when it grows larger, providing the best performance characteristics for both scenarios.

Syntax

Following is the syntax for creating a HybridDictionary with specified initial size −

HybridDictionary dict = new HybridDictionary(initialSize);

Where initialSize is an integer indicating the approximate number of entries the HybridDictionary can initially contain.

How It Works

The HybridDictionary automatically chooses the most efficient internal data structure based on the initial size parameter:

• If initial size is small (? 6), it starts with a ListDictionary

• If initial size is larger, it directly uses a Hashtable

• It can switch from ListDictionary to Hashtable as items are added

Using HybridDictionary with Small Initial Size

Example

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

public class Demo {
   public static void Main(){
      HybridDictionary dict = new HybridDictionary(5);
      dict.Add("A", "AB");
      dict.Add("B", "BC");
      dict.Add("C", "DE");
      dict.Add("D", "FG");
      dict.Add("E", "HI");
      Console.WriteLine("Key/Value pairs...");
      foreach(DictionaryEntry d in dict)
         Console.WriteLine("Key = "+d.Key + ", Value = " + d.Value);
   }
}

The output of the above code is −

Key/Value pairs...
Key = A, Value = AB
Key = B, Value = BC
Key = C, Value = DE
Key = D, Value = FG
Key = E, Value = HI

Using HybridDictionary with Large Initial Size

Example

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

public class Demo {
   public static void Main(){
      HybridDictionary dict = new HybridDictionary(10);
      dict.Add("1", 100);
      dict.Add("2", 200);
      dict.Add("3", 300);
      dict.Add("4", 400);
      dict.Add("5", 500);
      dict.Add("6", 600);
      dict.Add("7", 700);
      dict.Add("8", 800);
      dict.Add("9", 900);
      dict.Add("10", 1000);
      Console.WriteLine("Key/Value pairs...");
      foreach(DictionaryEntry d in dict)
         Console.WriteLine("Key = "+d.Key + ", Value = " + d.Value);
   }
}

The output of the above code is −

Key/Value pairs...
Key = 10, Value = 1000
Key = 1, Value = 100
Key = 2, Value = 200
Key = 3, Value = 300
Key = 4, Value = 400
Key = 5, Value = 500
Key = 6, Value = 600
Key = 7, Value = 700
Key = 8, Value = 800
Key = 9, Value = 900

Comparison with Other Collections

Conclusion

The HybridDictionary with specified initial size provides automatic performance optimization by choosing the best internal data structure. It starts with a ListDictionary for small collections and switches to a Hashtable for larger ones, making it ideal when the collection size varies or is unknown at compile time.