DispatcherObject.CheckAccess メソッド

定義

呼び出し元のスレッドがこの DispatcherObject にアクセスできるかどうかを確認します。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

戻り値

Boolean

呼び出し元のスレッドがこのオブジェクトにアクセスできる場合は true。それ以外の場合は falsetrue if the calling thread has access to this object; otherwise, false.

次の例では、CheckAccess を使用して、Button が作成されたスレッドにスレッドがアクセスできるかどうかを判断します。The following example uses CheckAccess to determine whether a thread has access to the thread that a Button was created on. ButtonCheckAccess メソッドを呼び出して、スレッドへのアクセスを確認します。The CheckAccess method on the Button is called to verify access to the thread. 呼び出し元のスレッドがアクセス権を持っている場合は、Buttonのメンバーにアクセスするだけで Button が更新されます。それ以外の場合は、引数として Button を受け取るデリゲートが ButtonDispatcher にポストされます。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

注釈

Dispatcher が作成されたスレッドだけが DispatcherObjectにアクセスできます。Only the thread the Dispatcher was created on may access the DispatcherObject.

どのスレッドも、この DispatcherObjectにアクセスできるかどうかを確認できます。Any thread can check to see whether it has access to this DispatcherObject.

CheckAccessVerifyAccess の違いは、CheckAccess は、呼び出し元のスレッドがこの DispatcherObject にアクセスできるかどうかを指定するブール値を返し、呼び出し元のスレッドがこの VerifyAccess にアクセスできない場合は例外をスローすることです。DispatcherObjectThe 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.

このメソッドの呼び出しは、関連付けられた Dispatcher オブジェクトで CheckAccess を呼び出すことと同じです。Calling this method is identical to calling CheckAccess on the associated Dispatcher object.

適用対象