select command on the gridview

[sanam]

Hello
I have a gridview that contain a template field I fill this template filed with this code :

   protected void GridView1_RowDataBound(object sender, GridViewRowEventArgs e)
    {
        
          if ((e.Row.RowType == DataControlRowType.DataRow ) & (e.Row.RowType!=DataControlRowType.Footer))
        { 
            DateTime datefromdb=Convert.ToDateTime(DataBinder.Eval(e.Row.DataItem,"date1"));
            
            System.Globalization.PersianCalendar PersianCalendar = new PersianCalendar();
            int daytoshamsi = PersianCalendar.GetDayOfMonth(datefromdb);
            int monthtoshamsi = PersianCalendar.GetMonth(datefromdb);
            int yeartoyear = PersianCalendar.GetYear(datefromdb);

            e.Row.Cells[5].Text = daytoshamsi+ "/" + monthtoshamsi + "/"+ yeartoyear;
        }

    }

I enable the selection on gridview and run it
when the page load template filed fill correctly.but when I click the select command on the gridview the content of template field disappear.why?
can anyone help me?