Dateset ds=new Dataset(); Datatable dt1=new Datatable("Table1"); Datatable dt2=new Datatable("Table1");ds.table.add(dt1); ds.table.add(dt2);DataRelation relation ; DataColumn table1Column ; DataColumn table2Column ;table1Column = ds.Tables["Table1"].Columns[0]; table2Column = ds.Tables["table2"].Columns[0];relation = new DataRelation("relation", table1Column, table2Column); ds.Relations.Add(relation);