silverlight user control events are not calling

 Hi all,
I have created a used control in silverlight
and add an event for image control
and use this control in page.xaml.
but event for its MouseLeftButtonDown is not calling i.e I have written in the coding for my_MouseLeftButtonUp function is not calling. I have also tried it for MouseLeftButtonDown but no affects

image 
<Image x:Name="my" MouseLeftButtonUp="my_MouseLeftButtonUp"  Width="20" Height="19" Grid.Row="0" Grid.Column="1" Margin="-6,5,6,-4"></Image> 
Can any one tell me the reason for that.
Sachin Mukhija 
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