How to update record in windows phone 8.

Question

I am developing windows phone 8 app.
I am having textbox and buttons and image in listbox.
When I added data to above columns then on click on button I am saving data in windows azure.
This is working fine.
when I click on image I am geting its index and all values related to it.
Now i can change these values if wants. and when click on button update query should get fire for selectes index.
How to find update query for selected index in WINDOWS PHONE 8
when click on button I want to fire update queryfor updating values of textbox in windows azure database.