How to add row to datatable or how to add row to grid row ASP.NET C#

//datarow and datatable

  protected void grdOpenVacancy_RowDeleting(object sender, GridViewDeleteEventArgs e)

        {

            int id = (int)grdOpenVacancy.DataKeys[e.RowIndex].Value;

            DataTable dtOpenVacancy = ViewState["vwOpenVacancy"] as DataTable;

            DataRow dr= dtOpenVacancy.AsEnumerable().Where(a=>a.Field<int>("ID") == id).FirstOrDefault();

            //GridViewRow grdrow = grdOpenVacancy.Rows[e.RowIndex];

            bool i = Repository.DeleteOpenVacancy(id);

            //            ddlCadreType_SelectedIndexChanged(null, null);

            

            if (ViewState["dt2"] != null)

            {

                DataTable dt3 = (DataTable)ViewState["dt2"];

                DataRow workRow = dt3.NewRow();

                // workRow["Institute"] = grdrow.Cells[0].Text;

                workRow["Institute"] = dr["InstituteName"];

                workRow["Discipline"] = dr["disciplineName"];

                workRow["cadrename"] = dr["cadreName"];

                workRow["cadreID"] = dr["cadreID"];

                workRow["SS"] = dr["SanctionedStrength"];

                workRow["IP"] = dr["inposition"];

                workRow["Vacancy"] = dr["vacancy"];

                dt3.Rows.Add(workRow);

                ViewState["dt2"] = dt3;

// grid row and grid view

//GridViewRow grdrow = grdOpenVacancy.Rows[e.RowIndex];

// workRow["Institute"] = grdrow.Cells[0].Text;

but in this case, grid column should have item template field.