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ArrayList.SyncRoot Property

Gets an object that can be used to synchronize access to the ArrayList.

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

'Declaration
Public Overridable ReadOnly Property SyncRoot As Object

Property Value

Type: System.Object
An object that can be used to synchronize access to the ArrayList.

Implements

ICollection.SyncRoot

To create a synchronized version of the ArrayList, use the Synchronized method. However, derived classes can provide their own synchronized version of the ArrayList using the SyncRoot property. The synchronizing code must perform operations on the SyncRoot of the ArrayList, not directly on the ArrayList. This ensures proper operation of collections that are derived from other objects. Specifically, it maintains proper synchronization with other threads that might be simultaneously modifying the ArrayList object.

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.


Dim myCollection As New ArrayList()

SyncLock myCollection.SyncRoot
    For Each item As Object In myCollection
        ' Insert your code here.
    Next item
End SyncLock


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

.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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

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