How to i display my data on a textbox when i click on the linkbutton on the gridview

Hello,
I create a gridview that bind with my database using linq and there is a link button in the gridview that i want to pass the data of a user to the textboxes. I try to use the CommandArgument=<%# Bind("Username") %> in my template fied but its not working.....Anyone cna help?

Heres my code for my Gridview :
<asp:GridView ID="GridView" runat="server" AutoGenerateColumns="False"> <Columns> <asp:TemplateField HeaderText="Username" InsertVisible="False" ShowHeader="False" > <ItemTemplate> <asp:LinkButton ID="linkbtn" runat="server" CommandName="username" OnClientClick="return GetData(this)" Text='<%# Eval("Username") %>' CommandArgument='<%# Bind("Username") %>' /> </ItemTemplate> </asp:TemplateField> <asp:TemplateField HeaderText="Fullname"> ...