DispatcherObject.CheckAccess Method

Definition

Determina si el subproceso de la llamada tiene acceso a DispatcherObject.Determines 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

Returns

Boolean

true si el subproceso de la llamada tiene acceso a este objeto; en caso contrario, false.true if the calling thread has access to this object; otherwise, false.

Examples

En el ejemplo siguiente se usa CheckAccess para determinar si un subproceso tiene acceso al subproceso en el que se creó un Button.The following example uses CheckAccess to determine whether a thread has access to the thread that a Button was created on. Se llama al método CheckAccess del Button para comprobar el acceso al subproceso.The CheckAccess method on the Button is called to verify access to the thread. Si el subproceso que realiza la llamada tiene acceso, el Button se actualiza simplemente teniendo acceso a los miembros del Button; de lo contrario, un delegado, que acepta un Button como argumento, se expone en el Dispatcher de la Button.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

Remarks

Solo el subproceso en el que se creó el Dispatcher puede tener acceso al DispatcherObject.Only the thread the Dispatcher was created on may access the DispatcherObject.

Cualquier subproceso puede comprobar si tiene acceso a este DispatcherObject.Any thread can check to see whether it has access to this DispatcherObject.

La diferencia entre CheckAccess y VerifyAccess es que CheckAccess devuelve un valor booleano que especifica si el subproceso que realiza la llamada tiene acceso a este DispatcherObject y VerifyAccess produce una excepción si el subproceso que realiza la llamada no tiene acceso a este 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.

Llamar a este método es idéntico a llamar a CheckAccess en el objeto Dispatcher asociado.Calling this method is identical to calling CheckAccess on the associated Dispatcher object.

Applies to