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

Définition

Détermine si le thread appelant a accès à ce 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

Retours

true si le thread appelant a accès à cet objet ; sinon, false.true if the calling thread has access to this object; otherwise, false.

Exemples

L’exemple suivant utilise CheckAccess pour déterminer si un thread a accès au thread sur Button lequel a été créé.The following example uses CheckAccess to determine whether a thread has access to the thread that a Button was created on. La CheckAccess méthodeButton sur est appelée pour vérifier l’accès au thread.The CheckAccess method on the Button is called to verify access to the thread. Si le thread appelant a accès, le Button est mis à jour en accédant simplement aux membres Buttonde; sinon, un délégué, qui accepte Button un comme Buttonargument, est publié sur le Dispatcher du.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

Remarques

Seul le thread Dispatcher sur lequel a été créé peut accéder DispatcherObjectau.Only the thread the Dispatcher was created on may access the DispatcherObject.

N’importe quel thread peut vérifier s’il a accès à ce DispatcherObject.Any thread can check to see whether it has access to this DispatcherObject.

La différence entre CheckAccess et VerifyAccess est que CheckAccess retourne une valeur booléenne qui spécifie si le thread appelant a accès DispatcherObject à VerifyAccess ce et lève une exception si le thread appelant n’a pas accès au Cela 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.

L’appel de cette méthode est identique CheckAccess à l’appel Dispatcher de sur l’objet associé.Calling this method is identical to calling CheckAccess on the associated Dispatcher object.

S’applique à