HybridDictionary. This C# collection attempts to optimize Hashtable. It switches from a linked list to a hash table when the number of elements increases past a certain threshold.

When you have a small number of elements, using an array can be faster to search. Computing the hash code takes longer than looping and testing each element.

An example. HybridDictionary is used in the same way as Hashtable. The HybridDictionary type is found in the System.Collections.Specialized namespace.

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

class Program
{
    static HybridDictionary GetHybridDictionary()
    {
        // Get and return HybridDictionary.
        HybridDictionary hybrid = new HybridDictionary();
        hybrid.Add("cat", 1);
        hybrid.Add("dog", 2);
        hybrid["rat"] = 0;
        return hybrid;
    }

    static void Main()
    {
        HybridDictionary hybrid = GetHybridDictionary();

        // Get values from HybridDictionary.
        int value1 = (int)hybrid["cat"];
        object value2 = hybrid["???"];
        object value3 = hybrid["dog"];
        int count1 = hybrid.Count;

        // Display values.
        Console.WriteLine(value1);
        Console.WriteLine(value2 == null);
        Console.WriteLine(value3);
        Console.WriteLine(count1);

        // Enumerate HybridDictionary.
        foreach (DictionaryEntry entry in hybrid)
        {
            Console.Write(entry.Key);
            Console.Write(": ");
            Console.WriteLine(entry.Value);
        }
    }
}
1
True
2
3
cat: 1
dog: 2
rat: 0

Generics. There is no collection that has the same change-over logic in the System.Collections.Generic namespace. Usually programs are better served with just a Dictionary.

We used HybridDictionary from System.Collections.Specialized. This C# type helps with small collections. But it is slower in many cases due to its internal logic.