Undo in RichTextBox does not undo Pasted Text

Question

I have a WinForms RichTextBox and by default the Undo works for most things, but when I Paste some Text in (I have stripped it of formatting it is just plain text), and try undo it does not undo the text just pasted.

Any help to a solution?

Answer 1

By design, a TextChanged event does not trigger the creation of an Undo state. Pasting triggers the TextChanged event, so that's why this is happening. To get around it,

I would recommend binding an event handler to the TextChanged event that invokes the KeyUp event. The KeyUp event does trigger the creation of Undo state creation.

Answer 2

Instead of replacing text explicitly, you can use the clipboard. And this wouldn't clear undo-stack

  var originalClbData = Clipboard.GetDataObject(); 
  Clipboard.SetText(newText);
  txtMailBody.SelectAll();
  txtMailBody.Paste();
  if (originalClbData != null) Clipboard.SetDataObject(originalClbData);