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DispatcherObject.CheckAccess Method

Determines whether the calling thread has access to this DispatcherObject.

Namespace:  System.Windows.Threading
Assembly:  WindowsBase (in WindowsBase.dll)

public bool CheckAccess()

Return Value

Type: System.Boolean
true if the calling thread has access to this object; otherwise, false.

Only the thread the Dispatcher was created on may access the DispatcherObject.

Any thread can check to see whether it has access to this DispatcherObject.

The difference between CheckAccess and VerifyAccess is that CheckAccess returns a Boolean that specifies whether the calling thread has access to this DispatcherObject and VerifyAccess throws an exception if the calling thread does not have access to the this DispatcherObject.

Calling this method is identical to calling CheckAccess on the associated Dispatcher object.

The following example uses CheckAccess to determine whether a thread has access to the thread that a Button was created on. The CheckAccess method on the Button is called to verify access to the thread. If the calling thread has access, the Button is updated by just accessing the members of the Button; otherwise, a delegate, which accepts a Button as an argument, is posted onto the Dispatcher of the Button.

// Uses the DispatcherObject.CheckAccess method to determine if 
// the calling thread has access to the thread the UI object is on
private void TryToUpdateButtonCheckAccess(object uiObject)
    Button theButton = uiObject as Button;

    if (theButton != null)
        // Checking if this thread has access to the object
            // This thread has access so it can update the UI thread
            // This thread does not have access to the UI thread
            // Pushing update method on the Dispatcher of the UI thread
                new UpdateUIDelegate(UpdateButtonUI), theButton);

.NET Framework

Supported in: 4, 3.5, 3.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, 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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