DispatcherObject.CheckAccess Metodo

Definizione

Determina se il thread chiamante ha accesso 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

Restituisce

true se il thread chiamate ha accesso a questo oggetto; in caso contrario, false.true if the calling thread has access to this object; otherwise, false.

Esempi

Nell'esempio seguente viene CheckAccess usato per determinare se un thread ha accesso al thread in cui Button è stato creato un oggetto.The following example uses CheckAccess to determine whether a thread has access to the thread that a Button was created on. Il CheckAccess metodoButton su viene chiamato per verificare l'accesso al thread.The CheckAccess method on the Button is called to verify access to the thread. Se il thread chiamante ha accesso, l' Button oggetto viene aggiornato semplicemente accedendo ai membri dell'oggetto Button; in caso contrario, un Button delegato, che accetta come Buttonargomento, viene pubblicato nell'oggetto Dispatcher della.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

Commenti

Solo il thread Dispatcher in cui è stato creato il può DispatcherObjectaccedere a.Only the thread the Dispatcher was created on may access the DispatcherObject.

Qualsiasi thread può verificare se ha accesso a questo DispatcherObject.Any thread can check to see whether it has access to this DispatcherObject.

La differenza tra CheckAccess e VerifyAccess è che CheckAccess restituisce un valore booleano che specifica se il thread chiamante ha accesso DispatcherObject a VerifyAccess questo e genera un'eccezione se il thread chiamante non ha accesso al questo 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.

La chiamata a questo metodo è identica CheckAccess alla chiamata sull' Dispatcher oggetto associato.Calling this method is identical to calling CheckAccess on the associated Dispatcher object.

Si applica a