Collections

.NET 1.1

What it Does	Java 2 (JDK 1.2+)	C#
Resizable Arrays	ArrayList	ArrayList
Linked Lists	LinkedList	ArrayList
Maps/Dictionaries	HashMap / Map	Hashtable
Stores Key/Value Pairs	SortedMap	SortedList

Note:

• Generics were introduced in .NET version 2.0

ArrayList

using System;
using System.Collections;

public class SamplesArrayList {

  public static void Main()  {

    // Creates and initializes a new ArrayList.
    ArrayList myAL = new ArrayList();
    myAL.Add("Hello");
    myAL.Add("World");
    myAL.Add("!");

    // Displays the properties and values of the ArrayList.
    Console.WriteLine( "myAL" );
    Console.WriteLine( "\tCount:    {0}", myAL.Count );
    Console.WriteLine( "\tCapacity: {0}", myAL.Capacity );
    Console.Write( "\tValues:" );
    PrintValues( myAL );
  }

  public static void PrintValues( IEnumerable myList )  {
    System.Collections.IEnumerator myEnumerator = myList.GetEnumerator();
    while (myEnumerator.MoveNext())
      Console.Write( "\t{0}", myEnumerator.Current);
    Console.WriteLine();
  }
}
/*
This code produces the following output.

myAL
    Count:    3
    Capacity: 16
    Values:    Hello    World    !
*/

Hashtable

…in .NET 2 use System.Collections.Generic.Dictionary…

.NET Framework Developer Center - Hashtable Class

using System.Collections;

Hashtable openWith = new Hashtable();

openWith.Add("txt", "notepad.exe");
openWith.Add("rtf", "wordpad.exe");

Console.WriteLine("For key = \"rtf\", value = {0}.", openWith["rtf"]);

if (openWith.ContainsKey("rtf"))
{
}

foreach( DictionaryEntry de in openWith )
{
  Console.WriteLine("Key = {0}, Value = {1}", de.Key, de.Value);
}

ICollection valueColl = openWith.Values;
foreach( string s in valueColl )
{
    Console.WriteLine("Value = {0}", s);
}

ICollection keyColl = openWith.Keys;
foreach( string s in keyColl )
{
    Console.WriteLine("Key = {0}", s);
}

openWith.Remove("rtf");

.NET 2

Dictionary

Replacing the Hashtable with Its Generic Counterpart Replace all occurrences of the System.Collections.Hashtable class with the faster generic System.Collections.Generic.Dictionary class.