How to set focus to a multi line textbox in silverlight 4 first line

Question

Hi,

      How to set focus of the cursor to the first line first character of a multi line textbox on "enter" click event in silvelight 4.
    Please help. its urgent. I tried with  txtDescription.SelectionStart = 0; and  txtDescription.SelectionLength = 0; but it is focus on second line first character.


Thanks,
Vijay