ToolStripDropDown.Opening イベントとは何？わかりやすく解説 Weblio辞書

.NET Framework クラスライブラリリファレンス

索引トップ用語の索引ランキング

ToolStripDropDown.Opening イベント

メモ : このイベントは、.NET Framework version 2.0 で新しく追加されたものです。

ToolStripDropDown コントロールが開くときに発生します。

名前空間: System.Windows.Forms
アセンブリ: System.Windows.Forms (system.windows.forms.dll 内)
構文

Visual Basic (宣言)

Public Event Opening As
 CancelEventHandler

Visual Basic (使用法)

Dim instance As ToolStripDropDown
Dim handler As CancelEventHandler

AddHandler instance.Opening, handler

public event CancelEventHandler Opening

C++

public:
event CancelEventHandler^ Opening {
    void add (CancelEventHandler^ value);
    void remove (CancelEventHandler^ value);
}

/** @event */
public void add_Opening (CancelEventHandler
 value)

/** @event */
public void remove_Opening (CancelEventHandler
 value)

JScript

JScript では、イベントは使用できますが、新規に宣言することはできません。

解説

イベント処理の詳細については、「イベントの利用」を参照してください。

使用例

Opening イベントを処理する方法を次の例に示します。

Visual Basic

' 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 Not (c Is Nothing)
 Then
            ' Add custom item (Form)
            fruitContextMenuStrip.Items.Add(("Source: "
 + c.GetType().ToString()))
        ElseIf Not (tsi Is
 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

// 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;
    }
}