DispatcherObject.CheckAccess DispatcherObject.CheckAccess DispatcherObject.CheckAccess DispatcherObject.CheckAccess Method

定义

确定调用线程是否可以访问此 DispatcherObjectDetermines whether the calling thread has access to this DispatcherObject.

public:
 bool CheckAccess();
public bool CheckAccess ();
member this.CheckAccess : unit -> bool
Public Function CheckAccess () As Boolean

返回

如果调用线程可以访问此对象,则为 true;否则,为 falsetrue if the calling thread has access to this object; otherwise, false.

示例

下面的示例使用CheckAccess来确定线程是否有权访问在上创建的线程ButtonThe following example uses CheckAccess to determine whether a thread has access to the thread that a Button was created on. CheckAccess 调用Button上的方法来验证对线程的访问。The CheckAccess method on the Button is called to verify access to the thread. 如果调用线程Button具有访问权限, 则只需访问的Button成员即可更新; 否则, 将在的上Dispatcher发布一个接受Button作为Button参数的委托。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);
        }
    }
}
' 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

注解

只有在上创建Dispatcher的线程可以DispatcherObject访问。Only the thread the Dispatcher was created on may access the DispatcherObject.

任何线程都可以检查它是否有权访问此DispatcherObjectAny thread can check to see whether it has access to this DispatcherObject.

CheckAccess CheckAccess DispatcherObject之间的区别在于, 返回一个布尔值, 该值指定调用线程是否有权访问此VerifyAccess值, 如果调用线程不具有访问权限, 则会引发异常。 VerifyAccessDispatcherObjectThe 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.

调用此方法与调用CheckAccess关联Dispatcher对象的方法相同。Calling this method is identical to calling CheckAccess on the associated Dispatcher object.

适用于