Hashtable Class

Represents a collection of key-and-value pairs that are organized based on the hash code of the key.

Definition

public class Hashtable: Object, IDictionary, ICloneable

Members Table

The following table lists the members exposed by the Hashtable object. Click a tab on the left to choose the type of member you want to view.

Methods

Method	Description
Add	Adds an element with the specified key and value into the Hashtable.
Clear	Removes all elements from the Hashtable.
Clone	Creates a shallow copy of the Hashtable.
Contains	Determines whether the Hashtable contains a specific key.
ContainsKey	Determines whether the Hashtable contains a specific key.
ContainsValue	Determines whether the Hashtable contains a specific value.
CopyTo	Copies the Hashtable elements to a one-dimensional Array instance at the specified index.
Equals	Overloaded. Compares two objects to determine if they are equal. (Inherited from Object)
GetEnumerator	Overloaded. (Inherited from IEnumerable)
GetHash	Returns the hash code for the specified key.
GetHashCode	Serves as a hash function for a particular type, suitable for use in hashing algorithms and data structures like a hash table. (Inherited from Object)
GetType	Gets the Type of the current instance. (Inherited from Object)
Hashtable	Overloaded. Initializes a new instance of Hashtable.
KeyEquals	Compares a specific Object with a specific key in the Hashtable.
ReferenceEquals	Determines whether the specified Object instances are the same instance. (Inherited from Object)
Remove	Removes the element with the specified key from the Hashtable.
Synchronized	Returns a synchronized wrapper for the Hashtable.
System.Collections.IEnumerable.GetEnumerator	Returns an IEnumerator that can iterate through the Hashtable.
ToString	Returns a String that represents the current Object. (Inherited from Object)
this[]	Gets or sets the value associated with the specified key.

Properties

Property	Description
Count	Gets the number of key-and-value pairs contained in the Hashtable.
IsFixedSize	Gets a value indicating whether the Hashtable has a fixed size.
IsReadOnly	Gets a value indicating whether the Hashtable is read-only.
IsSynchronized	Gets a value indicating whether access to the Hashtable is synchronized.
Keys	Gets an ICollection containing the keys in the Hashtable.
SyncRoot	Gets an object that can be used to synchronize access to the Hashtable.
Values	Gets an ICollection containing the values in the Hashtable.
comparer	Gets or sets the comparer to use for the Hashtable.
hcp	Gets or sets the object that can dispense hash codes for the Hashtable.

Inheritance Hierarchy

Object

Hashtable

Examples

Copy Code to Clipboard

// This examples shows how to create and initialize a Hashtable.

// It shows also some properties and method of the Hashtable class.

 

using System;

using System.Diagnostics;

using System.Collections;

 

public class SampleHashtable

{

     static void Main()

     {

          // Creates and initializes a new Hashtable.

          Hashtable myHT = new Hashtable();

 

          // Adds elements to the Hashtable.

          myHT.Add("First" , "Hello");

          myHT.Add("Second", "World");

          myHT.Add("Third", "!");

          myHT.Add("Fourth", "Hi");

          myHT.Add("Fifth", "Bye");

 

          // Displays the properties and values of the Hashtable.

          Debug.WriteLine("\nProperties of the collection:");

 

          bool FS = myHT.IsFixedSize;

          Debug.WriteLine("\tFixed size:"+FS.ToString());

 

          bool RO = myHT.IsReadOnly;

          Debug.WriteLine("\tRead only:"+RO.ToString());

 

          // Displays the contents of the Hashtable.

          Debug.WriteLine("\nInitial contents of the Hashtable:");

          DisplayValues(myHT);

 

          // Searches the Hashtable with Contains.

          bool t =myHT.Contains("Third");

          Debug.WriteLine("\n"+@"Contains ""Third""(using the Contains method):"+t.ToString());

 

          bool t1 =myHT.ContainsKey("First");

          Debug.WriteLine("\n"+@"Contains ""First""(using the ContainsKey method):"+t1.ToString());

 

          bool t2 =myHT.ContainsValue("Bye");

          Debug.WriteLine("\n"+@"Contains ""Bye""(using the ContainsValue method):"+t2.ToString());

 

          // Creates and displays the contents of an array of string.

          string[] myStrArray = new string[5] { "abc", "def", "ghi", "jkl", "mno" };

          Debug.Write("\nContents of an array of string:");

          DisplayArrayValues(myStrArray);

 

          // Copies the keys of the Hashtable to the array of string.

          myHT.Keys.CopyTo(myStrArray,0);

          Debug.Write("\n\nContents of the array after copying the keys of the collection in it:");

          DisplayArrayValues(myStrArray);

 

          // Removes an element from the Hashtable.

          myHT.Remove(4);

          Debug.WriteLine("\n\n"+@"Contents of the collection after removing the key ""4"":");

          DisplayValues2(myHT);

     }

 

     // Displays values using Keys property and the this[] method.

     public static void DisplayValues( Hashtable myHashtable )

     {

          ICollection myKeys = myHashtable.Keys;

          foreach ( object k in myKeys )

               Debug.WriteLine("\t"+k+":"+myHashtable[k].ToString());

     }

 

     // Displays values using an enumerator.

     public static void DisplayValues2( Hashtable myHashtable )

     {

          DictionaryEntry myDE;

          System.Collections.IEnumerator myEnumerator = myHashtable.GetEnumerator();

          while ( myEnumerator.MoveNext() )

               if ( myEnumerator.Current != null )

                    myDE = (DictionaryEntry) myEnumerator.Current;

                    Debug.WriteLine("\t"+myDE.Key.ToString()+":"+myDE.Value.ToString());

     }

 

     // Displays values using the foreach statement.

     public static void DisplayValues3 ( Hashtable myHashtable )

     {

          foreach ( DictionaryEntry myDE in myHashtable )

               Debug.WriteLine("\t"+myDE.Key.ToString()+":"+myDE.Value.ToString());

     }

 

     // Displays the values of an array.

     public static void DisplayArrayValues ( Array array )

     {

          for ( int i = 0; i < array.Length; i++ )

          {

               Debug.Write(array.GetValue(i)+" ");

          }

     }

}

 

 

/*

 

The output of the sample.

 

Properties of the collection:

     Fixed size:False

     Read only:False

 

Initial contents of the Hashtable:

     Fifth:Bye

     First:Hello

     Second:World

     Fourth:Hi

     Third:!

 

Contains "Third"(using the Contains method):True

Contains "First"(using the ContainsKey method):True

Contains "Bye"(using the ContainsValue method):True

 

Contents of an array of string:abc def ghi jkl mno

Contents of the array after copying the keys of the collection in it:Third Fourth Second First Fifth

 

Contents of the collection after removing the key "4":

     Fifth:Bye

     First:Hello

     Second:World

     Fourth:Hi

     Third:!

 

*/

Class Information

Namespace	System.Collections
Flash Library	corlib.scl
Flash Library Version	2.0.0.2466
Silverlight Library	System.Windows.Forms.dll