protected void Get_guard_shift_types()
        {
            DataTable dt = Guard_deployment.Return_guard_shift_types("return_guard_shift_types");

            if (dt.Rows.Count > 0)
            {
                DataRow dtRow = dt.NewRow();
                dtRow["shift_name"] = string.Empty;
                dtRow["shift_id"]   = -1;
                dt.Rows.InsertAt(dtRow, 0);
                this.cbo_working_shift.DataSource    = dt;
                this.cbo_working_shift.DisplayMember = "shift_name";
                this.cbo_working_shift.ValueMember   = "shift_id";
            }
        }