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Hashtable.SyncRoot Property

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

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

'Declaration
Public Overridable ReadOnly Property SyncRoot As Object
'Usage
Dim instance As Hashtable
Dim value As Object

value = instance.SyncRoot

/** @property */
public Object get_SyncRoot ()

public function get SyncRoot () : Object

Not applicable.

Property Value

An object that can be used to synchronize access to the Hashtable.

To create a synchronized version of the Hashtable, use the Synchronized method. However, derived classes can provide their own synchronized version of the Hashtable using the SyncRoot property. The synchronizing code must perform operations on the SyncRoot of the Hashtable, not directly on the Hashtable. 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 Hashtable 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 Hashtable()
 Dim item As Object
 SyncLock myCollection.SyncRoot
  For Each item In myCollection
  ' Insert your code here.
  Next item
 End SyncLock

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

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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