grid updation

Question

here it is my class grid


protected void gvclass_RowUpdating1(object sender, GridViewUpdateEventArgs e)
        {
            classinfo infoclass = new classinfo();
            classsp spclass = new classsp();
            GridViewRow row = gvclass.Rows[e.RowIndex];
            infoclass.classId = decimal.Parse(gvclass.DataKeys[e.RowIndex].Value.ToString());
            infoclass.className = ((TextBox)row.FindControl("txtclassname")).Text;
            infoclass.noOfSeats = int.Parse(((TextBox)row.FindControl("txtno")).Text);
            int a = spclass.ClassEdit(infoclass);
            gvclass.EditIndex = -1;
            gridfill();
           
        }



after clicking editt




gettin' error