How to make a button inside a gridview cause a partial post back and update my panel

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ASP.NET

C#3.5

Gridview

buttons

, +

i have an update panel with a gridview. The gridview consists of a button column. I want everytime this button is clicked, the update panel should be refreshed. From what i have been able to achieve, the buttton works fine but i would only be able to see the effect when i refreshed the whole page again. I need to see the effect on the click event without refreshing the page. How do i make this gridview button cause partial postback

What I have tried:

<pre lang="ASP.NET"><asp:TemplateField HeaderText="Action" Visible="True">
                               <ItemTemplate>
                                   <asp:Button Visible='<%# string.IsNullOrEmpty(Eval("Signout_Time").ToString()) %>' ID="out" runat="server" Text="Sign out" CommandName="SignOut"  CommandArgument='<%#Eval("SN") %>' ClientIDMode="AutoID"/>
                               </ItemTemplate>
                           </asp:TemplateField>

This is the code behind.

protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
       {
           if (e.Row.RowType == DataControlRowType.DataRow)
           {
               Button lb = e.Row.FindControl("out") as Button;
               ScriptManager.GetCurrent(this).RegisterAsyncPostBackControl(lb);
           }
    }

this is what the button does when i click

protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
       {
          if (e.CommandName == "SignOut")
           {
               string sN = e.CommandArgument.ToString();
               reg.sn = int.Parse(sN);
           string sign = System.DateTime.Now.ToString("yyyy-MM-dd:HH:mm:ss"); // get time out time
           reg.signout = sign;
           reg.SignOut(); // Save the signout time in db

After the whole process, i want the button to update only the updatepanel.