Dispatcher.CheckAccess メソッド

定義

呼び出し元のスレッドがこの Dispatcher に関連付けられたスレッドであるかどうかを判断します。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

戻り値

Boolean

呼び出し元のスレッドがこの Dispatcher に関連付けられたスレッドである場合は true。それ以外の場合は falsetrue if the calling thread is the thread associated with this Dispatcher; otherwise, false.

次の例では、を使用して CheckAccess 、スレッドがにアクセスできるかどうかを判断し Button ます。The following example uses CheckAccess to determine whether a thread has access to a Button. CheckAccess Dispatcher 関連付けられているのメソッドを Button 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 Dispatcher associated with the Button is called to verify access to the thread. 呼び出し元のスレッドがにアクセスできる場合 Dispatcher 、は Button のメンバーにアクセスすることによって更新されます Button 。それ以外の場合は、を Button 引数として受け取るデリゲートがに配置され Dispatcher ます。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. は、の Dispatcher 更新作業を委任し Button ます。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

注釈

によって作成され Dispatcher ただけ DispatcherObject がオブジェクトにアクセスできます。Only the Dispatcher that a DispatcherObject is created on may access the object. Invoke別の BeginInvoke スレッドからオブジェクトにアクセスするには、またはを使用します。Use Invoke or BeginInvoke to access the object from a different thread.

CheckAccess 任意のスレッドから呼び出すことができます。CheckAccess can be called from any thread.

との違い CheckAccess VerifyAccess は、 CheckAccess 呼び出し元のスレッドがにアクセスできるかどうかを示すブール値を返し、 Dispatcher 例外をスローし VerifyAccess ます。The 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.

適用対象

こちらもご覧ください