I got the error when i have load the data from gridview row command 
i have to load the textbox data from datatable then i got the error 
 AjaxControlToolkit.DLL!AjaxToolkit.ScriptControlBase.OnPreRender(System.EventArgs e) 

My code is below
if (e.CommandName == "Edit_G") { // std_id = Convert.ToInt32(e.CommandArgument.ToString()); std_id = 3; college_id=Convert.ToInt32(Session["college"].ToString()); academic_year_id=Convert.ToInt32(Session["academic_year"].ToString()); edit_student(std_id,college_id,academic_year_id); }



public void edit_student(int std_id,int college_id,int academic_year_id) { DataTable dt = new DataTable(); StringBuilder strBldr = new StringBuilder(); strBldr.Append("sp_student_registration"); SqlParameter[] sqlPrmt = new SqlParameter[] { new SqlParameter ( ...

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