Gets a value indicating whether the user can undo the previous operation in a text box control.
[Visual Basic] Public ReadOnly Property CanUndo As Boolean [C#] public bool CanUndo {get;} [C++] public: __property bool get_CanUndo(); [JScript] public function get CanUndo() : Boolean;
true if the user can undo the previous operation performed in a text box control; otherwise, false.
If this method returns true, you can call the Undo method to undo the last operation in a text box. You can use this method in the System.WinForms.MenuItem.Popup event of a MenuItem, or in code that manages the state of buttons on a System.WinForms.Toolbar to enable or disable the ability to undo the previous operation in a text box control.
The following example uses TextBox, a derived class. It provides System.WinForms.MenuItem.Click event-handling methods for MenuItem objects that perform Cut, Copy, Paste, and Undo operations. This example assumes that a TextBox control named Text1 has been created.
[Visual Basic]
Private Sub Menu_Copy(ByVal sender As System.Object, ByVal e As System.EventArgs) ' Ensure that text is selected in the text box. If Text1.SelectionLength > 0 Then ' Copy the selected text to the Clipboard. Text1.Copy End If End Sub Private Sub Menu_Cut(ByVal sender As System.Object, ByVal e As System.EventArgs) ' Ensure that text is currently selected in the text box. If Not Text1.SelectedText = "" Then ' Cut the currently selected text to in text box to Clipboard. Text1.Cut End If End Sub Private Sub Menu_Paste(ByVal sender As System.Object, ByVal e As System.EventArgs) ' Determine if there is any text in the Clipboard to paste into the text box. If Clipboard.GetDataObject.GetDataPresent(DataFormats.CF_STRINGCLASS) = True Then ' Determine if any text is selected in the text box. If Text1.SelectionLength > 0 Then ' Ask user if they want to paste over currently selected text. If MessageBox.Show("Do you want to paste over current selection?", "Cut Example", MessageBox.YesNo) = System.WinForms.DialogResult.No Then ' Move selection to the point after the current selection and paste. Text1.SelectionStart = Text1.SelectionStart + Text1.SelectionLength End If End If ' Paste current text in Clipboard into text box. Text1.Paste End If End Sub Private Sub Menu_Undo(ByVal sender As System.Object, ByVal e As System.EventArgs) ' Determine if we can undo last operation in text box. If Text1.CanUndo = True Then ' Undo the last operation. Text1.Undo ' Clear the undo buffer to prevent last action from being redone. Text1.ClearUndo End If End Sub
TextBoxBase Class | TextBoxBase Members | System.WinForms Namespace | Cut | Copy | Paste | Undo | Clear