ButtonClick in DropDown not working in VS2010/Outlook2010

I'm working on an add-in for Outlook 2010. I've created a new Ribbon Tab with a dropdown box. I'd like for the data in the dropdown to update when I click the dropdown button, but nothing is occurring. I've written the sample code below for testing purposes and nothing fires:

        private void dropDown1_ButtonClick(object sender, RibbonControlEventArgs e)
    {
        MessageBox.Show("Dropdown CLick");
    }

This is as simple as it gets, but nothing is firing. Any ideas of what I might be doing wrong? Th开发者_开发问答e only other code that exists in this ribbon right now is what loads the data.

Thank you

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From my understanding

private void dropDown1_Click(object sender, RibbonControlEventArgs e)
{
    MessageBox.Show("Dropdown CLick");
}

is what you wanna do. No where did I see ButtonClick as the proper tag.