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Vorgehensweise: Behandeln des Opening-Ereignisses von ContextMenuStrip

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Sie können das Verhalten Ihres ContextMenuStrip-Steuerelements anpassen, indem Sie das Opening-Ereignis behandeln.

Beispiel

Das folgende Codebeispiel veranschaulicht die Behandlung des Opening-Ereignisses. Der Ereignishandler fügt Elemente dynamisch zu einem ContextMenuStrip-Steuerelement hinzu. Das vollständige Codebeispiel finden Sie unter Vorgehensweise: Dynamisches Hinzufügen von ToolStrip-Elementen.

// This event handler is invoked when the ContextMenuStrip
// control's Opening event is raised. It demonstrates
// dynamic item addition and dynamic SourceControl
// determination with reuse.
void cms_Opening(object sender, System.ComponentModel.CancelEventArgs e)
{
    // Acquire references to the owning control and item.
    Control c = fruitContextMenuStrip.SourceControl as Control;
    ToolStripDropDownItem tsi = fruitContextMenuStrip.OwnerItem as ToolStripDropDownItem;

    // Clear the ContextMenuStrip control's Items collection.
    fruitContextMenuStrip.Items.Clear();

    // Check the source control first.
    if (c != null)
    {
        // Add custom item (Form)
        fruitContextMenuStrip.Items.Add("Source: " + c.GetType().ToString());
    }
    else if (tsi != null)
    {
        // Add custom item (ToolStripDropDownButton or ToolStripMenuItem)
        fruitContextMenuStrip.Items.Add("Source: " + tsi.GetType().ToString());
    }

    // Populate the ContextMenuStrip control with its default items.
    fruitContextMenuStrip.Items.Add("-");
    fruitContextMenuStrip.Items.Add("Apples");
    fruitContextMenuStrip.Items.Add("Oranges");
    fruitContextMenuStrip.Items.Add("Pears");

    // Set Cancel to false.
    // It is optimized to true based on empty entry.
    e.Cancel = false;
}

' This event handler is invoked when the ContextMenuStrip
' control's Opening event is raised. It demonstrates
' dynamic item addition and dynamic SourceControl 
' determination with reuse.
 Sub cms_Opening(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs)

     ' Acquire references to the owning control and item.
     Dim c As Control = fruitContextMenuStrip.SourceControl
     Dim tsi As ToolStripDropDownItem = fruitContextMenuStrip.OwnerItem 

     ' Clear the ContextMenuStrip control's 
     ' Items collection.
     fruitContextMenuStrip.Items.Clear()

     ' Check the source control first.
     If (c IsNot Nothing) Then
         ' Add custom item (Form)
         fruitContextMenuStrip.Items.Add(("Source: " + c.GetType().ToString()))
     ElseIf (tsi IsNot Nothing) Then
         ' Add custom item (ToolStripDropDownButton or ToolStripMenuItem)
         fruitContextMenuStrip.Items.Add(("Source: " + tsi.GetType().ToString()))
     End If

     ' Populate the ContextMenuStrip control with its default items.
     fruitContextMenuStrip.Items.Add("-")
     fruitContextMenuStrip.Items.Add("Apples")
     fruitContextMenuStrip.Items.Add("Oranges")
     fruitContextMenuStrip.Items.Add("Pears")

     ' Set Cancel to false. 
     ' It is optimized to true based on empty entry.
     e.Cancel = False
 End Sub

Legen Sie die CancelEventArgs.Cancel-Eigenschaft auf true fest, um zu verhindern, dass das Menü geöffnet wird.

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