Dennis,
There is an easier way to do what you want within the confines of the
..NET Framework. However, it isn't as far-reaching as you describe, but
then maybe you don't need such a wide-ranging solution as trapping
Windows messages would give you.
You can re-create the existing context menu in code and add items to
your re-created menu. You can then either: 1) Attach this to the text
boxes that require your new context menu, or 2) Create a sub-class of
TextBox that uses your new context menu and add that sub-class to your
forms in place of TextBox. Either way you will get a text box with what
looks like the standard context menu with one or more additional items.
Here is my code that re-creates the standard text box context menu:
using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;
namespace MyProject.Controls
{
/// <summary>
/// A home-grown version of the standard right-click context menu,
/// so that applications can extend this menu and add their own
/// context items.
/// </summary>
public class StandardTextBoxContextMenu : ContextMenu
{
private System.Windows.Forms.MenuItem miUndo;
private System.Windows.Forms.MenuItem miCut;
private System.Windows.Forms.MenuItem miCopy;
private System.Windows.Forms.MenuItem miPaste;
private System.Windows.Forms.MenuItem miDelete;
private System.Windows.Forms.MenuItem miSelectAll;
private System.Windows.Forms.MenuItem miSeparator;
/// <summary>
/// Creates a standard context menu for a text box, containing
/// Undo, Cut, Copy, Paste... all of the usual context menu
/// items.
/// </summary>
public StandardTextBoxContextMenu() : this(new MenuItem[0])
{ }
/// <summary>
/// Creates a standard context menu for a text box, containing
/// Undo, Cut, Copy, Paste... all of the usual context menu
/// items, with additional menu items supplied by the caller
/// that will precede the standard items in the context menu.
/// </summary>
/// <param name="additionalMenuItems">Menu items that should
/// appear above the standard menu items.</param>
/// <remarks>You can get the same effect as calling this
/// constructor by calling the no parameter constructor
/// and then using <see cref="Menu.MenuItemCollection.AddRange"/>
/// to add menu items later. Just set the <see
cref="MenuItem.Index"/>
/// property of the menu items to start numbering from
/// 0, and <see cref="Menu.MenuItemCollection.AddRange"/> will
rearrange
/// the standard menu items to follow the new ones you add.</remarks>
public StandardTextBoxContextMenu(MenuItem[] additionalMenuItems)
{
this.MenuItems.AddRange(additionalMenuItems);
InitializeComponent();
}
private void InitializeComponent()
{
this.miUndo = new System.Windows.Forms.MenuItem();
this.miSeparator = new System.Windows.Forms.MenuItem();
this.miCut = new System.Windows.Forms.MenuItem();
this.miCopy = new System.Windows.Forms.MenuItem();
this.miPaste = new System.Windows.Forms.MenuItem();
this.miDelete = new System.Windows.Forms.MenuItem();
this.miSelectAll = new System.Windows.Forms.MenuItem();
//
// miUndo
//
this.miUndo.Text = "&Undo";
this.miUndo.Click += new System.EventHandler(this.miUndo_Click);
//
// miSeparator
//
this.miSeparator.Text = "-";
//
// miCut
//
this.miCut.Text = "Cu&t";
this.miCut.Click += new System.EventHandler(this.miCut_Click);
//
// miCopy
//
this.miCopy.Text = "&Copy";
this.miCopy.Click += new System.EventHandler(this.miCopy_Click);
//
// miPaste
//
this.miPaste.Text = "&Paste";
this.miPaste.Click += new System.EventHandler(this.miPaste_Click);
//
// miDelete
//
this.miDelete.Text = "&Delete";
this.miDelete.Click += new System.EventHandler(this.miDelete_Click);
//
// miSelectAll
//
this.miSelectAll.Text = "Select &All";
this.miSelectAll.Click += new
System.EventHandler(this.miSelectAll_Click);
this.MenuItems.AddRange(
new System.Windows.Forms.MenuItem[] {
this.miUndo,
this.miSeparator,
this.miCut,
this.miCopy,
this.miPaste,
this.miDelete,
this.miSelectAll
});
this.Popup += new EventHandler(StandardTextBoxContextMenu_Popup);
}
private void miUndo_Click(object sender, System.EventArgs e)
{
// Get the text box that the context menu was popped on
if (this.SourceControl is TextBox)
{
TextBox clickedBox = (TextBox)this.SourceControl;
if (clickedBox.CanUndo)
{
clickedBox.Undo();
}
}
}
private void miCut_Click(object sender, System.EventArgs e)
{
// Get the text box that the context menu was popped on
if (this.SourceControl is TextBox)
{
TextBox clickedBox = (TextBox)this.SourceControl;
if (clickedBox.SelectionLength > 0)
{
clickedBox.Cut();
}
}
}
private void miCopy_Click(object sender, System.EventArgs e)
{
// Get the text box that the context menu was popped on
if (this.SourceControl is TextBox)
{
TextBox clickedBox = (TextBox)this.SourceControl;
if (clickedBox.SelectionLength > 0)
{
clickedBox.Copy();
}
}
}
private void miPaste_Click(object sender, System.EventArgs e)
{
// Get the text box that the context menu was popped on
if (this.SourceControl is TextBox)
{
TextBox clickedBox = (TextBox)this.SourceControl;
if (clickedBox.SelectionLength > 0)
{
clickedBox.Paste();
}
}
}
[DllImport("user32.dll", CharSet = CharSet.Auto)]
private static extern int SendMessage(System.IntPtr hWnd, int msg,
int lParam, int wParam);
private const int WM_CLEAR = 0x0303;
private void miDelete_Click(object sender, System.EventArgs e)
{
// Get the text box that the context menu was popped on
if (this.SourceControl is TextBox)
{
TextBox clickedBox = (TextBox)this.SourceControl;
if (clickedBox.SelectionLength > 0)
{
SendMessage(clickedBox.Handle, WM_CLEAR, 0, 0);
}
}
}
private void miSelectAll_Click(object sender, System.EventArgs e)
{
// Get the text box that the context menu was popped on
if (this.SourceControl is TextBox)
{
TextBox clickedBox = (TextBox)this.SourceControl;
clickedBox.SelectAll();
}
}
private void StandardTextBoxContextMenu_Popup(object sender,
EventArgs e)
{
// Get the text box that the context menu was popped on
if (this.SourceControl is TextBox)
{
TextBox clickedBox = (TextBox)this.SourceControl;
// Enable and disable standard menu items as necessary
bool isSelection = clickedBox.SelectionLength > 0;
IDataObject clipObject = Clipboard.GetDataObject();
bool textOnClipboard = clipObject.GetDataPresent(DataFormats.Text);
this.miUndo.Enabled = clickedBox.CanUndo;
this.miCut.Enabled = isSelection;
this.miCopy.Enabled = isSelection;
this.miPaste.Enabled = textOnClipboard;
this.miDelete.Enabled = isSelection;
}
}
}
}
