how to calculate datagridview row value and shown in an another datagridview

DataTable dt = new DataTable();
           DataRow dr = dt.NewRow();
           dt.Columns.Add("code", typeof(int));
           dt.Columns.Add("Tax", typeof(int));
           dt.Columns.Add("Amount", typeof(decimal));
           dr["code"] = 1;
           dr["tax"] = 3;
           dr["Amount"] = 0.73;
           dt.Rows.Add(dr);
           DataRow dr1 = dt.NewRow();
           dr1["code"] = 2;
           dr1["tax"] =4;
           dr1["Amount"] =1.3;
           dt.Rows.Add(dr1);
           DataRow dr2 = dt.NewRow();
           dr2["code"] = 3;
           dr2["tax"] = 3;
           dr2["Amount"] = 0.92;
           dt.Rows.Add(dr2);
           DataTable dt1 = new DataTable();

           dt1.Columns.Add("Tax", typeof(int));
           dt1.Columns.Add("TotalAmount", typeof(decimal));

           var query = from row in dt.AsEnumerable()
                       group row by row.Field<int>("Tax") into grp
                       select new
                       {
                           tax = grp.Key,
                           sum = grp.Sum(r => r.Field<decimal>("Amount"))
                       };
           foreach (var grp in query)
           {
               DataRow row = dt1.NewRow();
               row["Tax"] = grp.tax;
               row["TotalAmount"] = grp.sum;
               dt1.Rows.Add(row);
           }