Question

I am building a kind of autocomplete text input using a WinForms ComboBox, and I need the autocompletion behavior to change depending on the position of the caret in the string.

However, the ComboBox doesn’t seem to expose an event to catch a change in the caret position. I can catch TextUpdated when the user is typing. But when the user is navigating, I need to handle KeyDown and check if the KeyCode is Left, Right, Home or End. However the event is fired before the caret is changed, so I would need to compute the new caret position. This is extremely annoying because this requires special handling when Ctrl is pressed and possibly if there are some special accessibility settings I don’t know about.

So I was wondering if there was a better way to do that. Is there an event that is fired each time the caret changes position in the ComboBox or is there a way I can execute code after the KeyDown event is handled by the ComboBox?

Answer 1

You can execute the code right after KeyDown processing:

  private void comboBox1_KeyDown(object sender, KeyEventArgs e)
  {
       BeginInvoke(new MethodInvoker(_CheckCaretPosition));
  }

  void _CheckCaretPosition()
  {
       int caretPosition = comboBox1.SelectionStart;
       Debug.WriteLine(caretPosition);
  }