DispatcherObject.CheckAccess Method ()
Determines whether the calling thread has access to this DispatcherObject.
Assembly: WindowsBase (in WindowsBase.dll)
Any thread can check to see whether it has access to this DispatcherObject.
The difference between VerifyAccess is that 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.and
The following example uses Button was created on. The 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.to determine whether a thread has access to the thread that a
' Uses the DispatcherObject.CheckAccess method to determine if ' the calling thread has access to the thread the UI object is on Private Sub TryToUpdateButtonCheckAccess(ByVal uiObject As Object) Dim theButton As Button = TryCast(uiObject, Button) If theButton IsNot Nothing Then ' Checking if this thread has access to the object If theButton.CheckAccess() Then ' This thread has access so it can update the UI thread UpdateButtonUI(theButton) Else ' This thread does not have access to the UI thread ' Pushing update method on the Dispatcher of the UI thread theButton.Dispatcher.BeginInvoke(DispatcherPriority.Normal, New UpdateUIDelegate(AddressOf UpdateButtonUI), theButton) End If End If End Sub
Available since 3.0