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ArrayList.IsSynchronized Property

Gets a value indicating whether access to the ArrayList is synchronized (thread safe).

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

public virtual bool IsSynchronized { get; }
/** @property */
public boolean get_IsSynchronized ()

public function get IsSynchronized () : boolean

Not applicable.

Property Value

true if access to the ArrayList is synchronized (thread safe); otherwise, false. The default is false.

To guarantee the thread safety of the ArrayList, all operations must be done through the wrapper returned by the Synchronized method.

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.

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

Retrieving the value of this property is an O(1) operation.

The following code example shows how to synchronize an ArrayList, determine if an ArrayList is synchronized and use a synchronized 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( "The" );
      myAL.Add( "quick" );
      myAL.Add( "brown" );
      myAL.Add( "fox" );

      // Creates a synchronized wrapper around the ArrayList.
      ArrayList mySyncdAL = ArrayList.Synchronized( myAL );

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

myAL is not synchronized.
mySyncdAL is synchronized.
*/ 

import System.*;
import System.Collections.*;

public class SamplesArrayList
{
    public static void main(String[] args)
    {
        // Creates and initializes a new ArrayList.
        ArrayList myAL = new ArrayList();

        myAL.Add("The");
        myAL.Add("quick");
        myAL.Add("brown");
        myAL.Add("fox");

        // Creates a synchronized wrapper around the ArrayList.
        ArrayList mySyncdAL = ArrayList.Synchronized(myAL);

        // Displays the sychronization status of both ArrayLists.
        Console.WriteLine("myAL is {0}.", myAL.get_IsSynchronized()
            ? "synchronized" : "not synchronized");
        Console.WriteLine("mySyncdAL is {0}.", mySyncdAL.get_IsSynchronized()
            ? "synchronized" : "not synchronized");
    } //main
} //SamplesArrayList
/* 
 This code produces the following output.
 
 myAL is not synchronized.
 mySyncdAL is synchronized.
 */

import System;
import System.Collections;

// Creates and initializes a new ArrayList.
var myAL : ArrayList = new ArrayList();
myAL.Add( "The" );
myAL.Add( "quick" );
myAL.Add( "brown" );
myAL.Add( "fox" );

// Creates a synchronized wrapper around the ArrayList.
var mySyncdAL : ArrayList  = ArrayList.Synchronized( myAL );

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

Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

.NET Compact Framework

Supported in: 2.0, 1.0

XNA Framework

Supported in: 1.0
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