Dispatcher.CheckAccess Méthode

Définition

Détermine si le thread appelant est le thread associé à ce 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

Retours

true si le thread appelant est le thread associé à ce Dispatcher ; sinon, false.true if the calling thread is the thread associated with this Dispatcher; otherwise, false.

Exemples

L’exemple suivant utilise CheckAccess pour déterminer si un thread a accès à un Button.The following example uses CheckAccess to determine whether a thread has access to a Button. La CheckAccess méthode sur le Dispatcher associé Button à est appelée pour vérifier l’accès au thread.The CheckAccess method on the Dispatcher associated with the Button is called to verify access to the thread. Si le thread Dispatcherappelant a accès au, le Button est mis à jour en accédant aux membres de Button; sinon, un délégué, qui accepte un Button comme argument, est placé sur Dispatcher.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. Le Dispatcher délègue le travail de Buttonmise à jour de.The 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

Remarques

Seul le Dispatcher sur lequel DispatcherObject un est créé peut accéder à l’objet.Only the Dispatcher that a DispatcherObject is created on may access the object. Utilisez Invoke ouBeginInvoke pour accéder à l’objet à partir d’un thread différent.Use Invoke or BeginInvoke to access the object from a different thread.

CheckAccesspeut être appelé à partir de n’importe quel thread.CheckAccess can be called from any thread.

La différence entre CheckAccess VerifyAccess Dispatcher et retourne une valeur booléenne indiquant si le thread appelant a accès à et VerifyAccess lève une exception. CheckAccessThe 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.

S’applique à

Voir aussi