How to force a WPF ComboBox to show its items list?

I have a Button and a hidden WPF ComboBox. When the b开发者_StackOverflowutton is pressed, the ComboBox must be shown and be ready to select an item from its list.

How can the ComboBox drop down list be forced to show programmatically?

To open the drop down.

    combo.IsDropDownOpen = true;

Have you tried:

ComboBox1.DroppedDown = True