problem in combobox inside usercontrol in wpf

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C#

C#4.0

i am using combobox inside usercontrol in wpf when i select the item in the combobox the control transfer
to the main page tab control and than again call the user control page , because of that i lost
the selected item in that combobox. other controls in that page are working properly.so anyone

idea about this what exactly the problem help me