Dispatcher.CheckAccess Método

Definición

Determina si el subproceso de la llamada es el subproceso asociado a este objeto Dispatcher.Determines whether the calling thread is the thread associated with this Dispatcher.

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

Devoluciones

Es true si el subproceso de la llamada es el subproceso asociado a este objeto Dispatcher; de lo contrario, es false.true if the calling thread is the thread associated with this Dispatcher; otherwise, false.

Ejemplos

En el ejemplo siguiente CheckAccess se usa para determinar si un subproceso tiene Buttonacceso a.The following example uses CheckAccess to determine whether a thread has access to a Button. Se llama al Dispatcher Button método en el asociado a la clase para comprobar el acceso al subproceso. CheckAccessThe CheckAccess method on the Dispatcher associated with the Button is called to verify access to the thread. Si el subproceso que realiza la llamada Dispatchertiene acceso Button a, se actualiza mediante el acceso a los Buttonmiembros de; de lo contrario, un delegado Button , que acepta un como argumento, se Dispatchercoloca en.If the calling thread has access to the Dispatcher, the Button is updated by accessing the members of the Button; otherwise, a delegate, which accepts a Button as an argument, is placed onto the Dispatcher. Delegará el trabajo de Buttonactualización de. DispatcherThe Dispatcher will delegate the work of updating the Button.

// Uses the Dispatcher.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.Dispatcher.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.
            // Place the update method on the Dispatcher of the UI thread.
            theButton.Dispatcher.BeginInvoke(DispatcherPriority.Normal,
                new UpdateUIDelegate(UpdateButtonUI), theButton);
        }
    }
}
' Uses the Dispatcher.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.Dispatcher.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.
            ' Place the 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

Comentarios

Solo el Dispatcher DispatcherObject que se crea en puede tener acceso al objeto.Only the Dispatcher that a DispatcherObject is created on may access the object. Use Invoke oBeginInvoke para tener acceso al objeto desde un subproceso diferente.Use Invoke or BeginInvoke to access the object from a different thread.

CheckAccessse puede llamar desde cualquier subproceso.CheckAccess can be called from any thread.

La diferencia entre CheckAccess y VerifyAccess es CheckAccess devuelve un valor booleano que indica Dispatcher si el subproceso que realiza la VerifyAccess llamada tiene acceso a y produce una excepción.The difference between CheckAccess and VerifyAccess is CheckAccess returns a Boolean indicating whether the calling thread has access to the Dispatcher and VerifyAccess throws an exception.

Se aplica a

Consulte también: