DispatcherObject.CheckAccess 方法

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

Boolean

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 Button 在上创建的线程。The following example uses CheckAccess to determine whether a thread has access to the thread that a Button was created on. CheckAccess调用上的方法 Button 来验证对线程的访问。The CheckAccess method on the Button is called to verify access to the thread. 如果调用线程具有访问权限,则 Button 只需访问的成员即可更新 Button ; 否则,将在的 Button 上发布一个接受作为参数的委托 Dispatcher ButtonIf 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 Dispatcher 在上创建的线程可以访问 DispatcherObjectOnly 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.

与之间的区别在于 CheckAccess VerifyAccessCheckAccess 返回一个布尔值,该值指定调用线程是否有权访问此值 DispatcherObjectVerifyAccess 如果调用线程没有访问此的权限,则会引发异常 DispatcherObjectThe 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 关联对象的方法相同 DispatcherCalling this method is identical to calling CheckAccess on the associated Dispatcher object.

适用于