ToolStripDropDown.Opening Ereignis

Definition

Tritt während des Öffnens von ToolStripDropDown auf.Occurs when the ToolStripDropDown control is opening.

public:
 event System::ComponentModel::CancelEventHandler ^ Opening;
public event System.ComponentModel.CancelEventHandler Opening;
member this.Opening : System.ComponentModel.CancelEventHandler 
Public Custom Event Opening As CancelEventHandler 

Beispiele

Im folgenden Beispiel wird veranschaulicht, wie das Opening-Ereignis behandelt wird.The following example demonstrates how to handle the Opening event.

// This code example demonstrates how to handle the Opening event.
// It also demonstrates dynamic item addition and dynamic 
// SourceControl determination with reuse.
class Form3 : Form
{
    // Declare the ContextMenuStrip control.
    private ContextMenuStrip fruitContextMenuStrip;

    public Form3()
    {
        // Create a new ContextMenuStrip control.
        fruitContextMenuStrip = new ContextMenuStrip();

        // Attach an event handler for the 
        // ContextMenuStrip control's Opening event.
        fruitContextMenuStrip.Opening += new System.ComponentModel.CancelEventHandler(cms_Opening);

        // Create a new ToolStrip control.
        ToolStrip ts = new ToolStrip();

        // Create a ToolStripDropDownButton control and add it
        // to the ToolStrip control's Items collections.
        ToolStripDropDownButton fruitToolStripDropDownButton = new ToolStripDropDownButton("Fruit", null, null, "Fruit");
        ts.Items.Add(fruitToolStripDropDownButton);

        // Dock the ToolStrip control to the top of the form.
        ts.Dock = DockStyle.Top;

        // Assign the ContextMenuStrip control as the 
        // ToolStripDropDownButton control's DropDown menu.
        fruitToolStripDropDownButton.DropDown = fruitContextMenuStrip;

        // Create a new MenuStrip control and add a ToolStripMenuItem.
        MenuStrip ms = new MenuStrip();
        ToolStripMenuItem fruitToolStripMenuItem = new ToolStripMenuItem("Fruit", null, null, "Fruit");
        ms.Items.Add(fruitToolStripMenuItem);

        // Dock the MenuStrip control to the top of the form.
        ms.Dock = DockStyle.Top;

        // Assign the MenuStrip control as the 
        // ToolStripMenuItem's DropDown menu.
        fruitToolStripMenuItem.DropDown = fruitContextMenuStrip;

        // Assign the ContextMenuStrip to the form's 
        // ContextMenuStrip property.
        this.ContextMenuStrip = fruitContextMenuStrip;

        // Add the ToolStrip control to the Controls collection.
        this.Controls.Add(ts);

        //Add a button to the form and assign its ContextMenuStrip.
        Button b = new Button();
        b.Location = new System.Drawing.Point(60, 60);
        this.Controls.Add(b);
        b.ContextMenuStrip = fruitContextMenuStrip;

        // Add the MenuStrip control last.
        // This is important for correct placement in the z-order.
        this.Controls.Add(ms);
    }

    // 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 code example demonstrates how to handle the Opening event.
' It also demonstrates dynamic item addition and dynamic 
' SourceControl determination with reuse.
Class Form3
    Inherits Form

   ' Declare the ContextMenuStrip control.
   Private fruitContextMenuStrip As ContextMenuStrip
   
   
   Public Sub New()
      ' Create a new ContextMenuStrip control.
      fruitContextMenuStrip = New ContextMenuStrip()
      
      ' Attach an event handler for the 
      ' ContextMenuStrip control's Opening event.
      AddHandler fruitContextMenuStrip.Opening, AddressOf cms_Opening
      
      ' Create a new ToolStrip control.
      Dim ts As New ToolStrip()
      
      ' Create a ToolStripDropDownButton control and add it
      ' to the ToolStrip control's Items collections.
      Dim fruitToolStripDropDownButton As New ToolStripDropDownButton("Fruit", Nothing, Nothing, "Fruit")
      ts.Items.Add(fruitToolStripDropDownButton)
      
      ' Dock the ToolStrip control to the top of the form.
      ts.Dock = DockStyle.Top
      
      ' Assign the ContextMenuStrip control as the 
      ' ToolStripDropDownButton control's DropDown menu.
      fruitToolStripDropDownButton.DropDown = fruitContextMenuStrip
      
      ' Create a new MenuStrip control and add a ToolStripMenuItem.
      Dim ms As New MenuStrip()
      Dim fruitToolStripMenuItem As New ToolStripMenuItem("Fruit", Nothing, Nothing, "Fruit")
      ms.Items.Add(fruitToolStripMenuItem)
      
      ' Dock the MenuStrip control to the top of the form.
      ms.Dock = DockStyle.Top
      
      ' Assign the MenuStrip control as the 
      ' ToolStripMenuItem's DropDown menu.
      fruitToolStripMenuItem.DropDown = fruitContextMenuStrip
      
      ' Assign the ContextMenuStrip to the form's 
      ' ContextMenuStrip property.
      Me.ContextMenuStrip = fruitContextMenuStrip
      
      ' Add the ToolStrip control to the Controls collection.
        Me.Controls.Add(ts)

        'Add a button to the form and assign its ContextMenuStrip.
        Dim b As New Button()
        b.Location = New System.Drawing.Point(60, 60)
        Me.Controls.Add(b)
        b.ContextMenuStrip = fruitContextMenuStrip
      
      ' Add the MenuStrip control last.
      ' This is important for correct placement in the z-order.
      Me.Controls.Add(ms)
    End Sub
   
   ' 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
End Class

Hinweise

Weitere Informationen zur Behandlung von Ereignissen finden Sie unter behandeln und Auslösen von Ereignissen.For more information about handling events, see Handling and Raising Events.

Gilt für: