Winforms: how to open combobox properly?

Question

I have a combobox on the winforms. On Enter even I open it:

cbo.DroppedDown = true;

But if I do that the combo opens and closes immediately

Answer 1

I tried it just like this:

private void comboBox1_enter(object sender, EventArgs e)
      {
         comboBox1.DroppedDown = true;
      }

no changes to mouseup or timers. it behaved just as expected. Whether I selected the comboBox with a mouse click or tabbed into it the drop down list appeared and stayed open until I selected something.

I would look to see if there is something else pulling focus off the box.