[wxPython] Newbie text ctrl question

wxPython Users
1

Trying to select (highlight) the text in a wxTextCtrl after user clicks a button.

I tried:

            self.txtOrderNum.SetSelection(-1, -1)

and

            self.txtOrderNum.SetSelection(0, len(self.txtOrderNum.GetValue()))

Both have no effect. I can SetValue with no problems.

Should be easy right? What am I missing?

TIA,

Bill