Export (0) Print
Expand All

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()
You cannot use methods in XAML.

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.

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 
        if(theButton.CheckAccess())
        {
            // 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(UpdateButtonUI), theButton);
        }
    }
}

Windows 7, Windows Vista, Windows XP SP2, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003

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

.NET Framework

Supported in: 3.5, 3.0

Community Additions

ADD
Show:
© 2014 Microsoft