WPF Combobox doesn't reply to keyboard inputs quickly

Question

Hi 

I have a simple WPF application which is having combobox on xaml. Following is the XAML code.

<ComboBox  Height="23" HorizontalAlignment="Left" Margin="21,25,0,0" Name="comboBox1" VerticalAlignment="Top" Width="120">

            <ComboBoxItem Content="Yes" />

            <ComboBoxItem Content="No" />

        </ComboBox>

The problem is Combo does not respond to keyboard  inputs quickly e.g. if you press any two keys immediately (Y & N ) one after the other instead of second only the first combo value get selected. So the problem is only when the multiple combo values are selected within a fraction of seconds.

Any help will be appreciated.

Thanks

Vinayak