Synchronized Method

Hashtable.Synchronized Method

Returns a synchronized (thread safe) wrapper for the Hashtable.

Namespace:  System.Collections
Assembly:  mscorlib (in mscorlib.dll)

[HostProtectionAttribute(SecurityAction.LinkDemand, Synchronization = true)]
public static Hashtable Synchronized(
	Hashtable table
)

Parameters

table
Type: System.Collections.Hashtable

The Hashtable to synchronize.

Return Value

Type: System.Collections.Hashtable
A synchronized (thread safe) wrapper for the Hashtable.

ExceptionCondition
ArgumentNullException

table is null.

NoteNote:

The HostProtectionAttribute attribute applied to this type or member has the following Resources property value: Synchronization. The HostProtectionAttribute does not affect desktop applications (which are typically started by double-clicking an icon, typing a command, or entering a URL in a browser). For more information, see the HostProtectionAttribute class or SQL Server Programming and Host Protection Attributes.

The Synchronized method is thread safe for multiple readers and writers. Furthermore, the synchronized wrapper ensures that there is only one writer writing at a time.

Enumerating through a collection is intrinsically not a thread-safe procedure. Even when a collection is synchronized, other threads can still modify the collection, which causes the enumerator to throw an exception. To guarantee thread safety during enumeration, you can either lock the collection during the entire enumeration or catch the exceptions resulting from changes made by other threads.

The following code example shows how to lock the collection using the SyncRoot during the entire enumeration:

Hashtable myCollection = new Hashtable();
  lock(myCollection.SyncRoot) {
  foreach (Object item in myCollection) {
  // Insert your code here.
  }
 }

This method is an O(1) operation.

The following example shows how to synchronize a Hashtable, determine if a Hashtable is synchronized, and use a synchronized Hashtable.

using System;
using System.Collections;
public class SamplesHashtable  {

   public static void Main()  {

      // Creates and initializes a new Hashtable.
      Hashtable myHT = new Hashtable();
      myHT.Add( 0, "zero" );
      myHT.Add( 1, "one" );
      myHT.Add( 2, "two" );
      myHT.Add( 3, "three" );
      myHT.Add( 4, "four" );

      // Creates a synchronized wrapper around the Hashtable.
      Hashtable mySyncdHT = Hashtable.Synchronized( myHT );

      // Displays the sychronization status of both Hashtables.
      Console.WriteLine( "myHT is {0}.", myHT.IsSynchronized ? "synchronized" : "not synchronized" );
      Console.WriteLine( "mySyncdHT is {0}.", mySyncdHT.IsSynchronized ? "synchronized" : "not synchronized" );
   }
}
/* 
This code produces the following output.

myHT is not synchronized.
mySyncdHT is synchronized.
*/

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98, Windows CE, Windows Mobile for Smartphone, Windows Mobile for Pocket PC, Xbox 360, Zune

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 3.5, 2.0, 1.0

XNA Framework

Supported in: 3.0, 2.0, 1.0

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