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?

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To open the drop down.

    combo.IsDropDownOpen = true;

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Have you tried:

ComboBox1.DroppedDown = True