I need to display a variable-length message and allow the text to be selectable. I have made the TextBox ReadOnly which does not allow the text to be edited, but the input c
AFAIK, this cannot be done. The TextBox control is a funny control because it actually has a lot of behaviour that can't be modified due to the way it taps into the operating system. This is why many of the cool custom TextBoxes are written from scratch.
I am afraid you may not be able to do what you wish to do :(