DataColumn dcEEmpID, dcSEmpID;

dcEEmpID= ds1.Tables["Emp"].Columns["EmpID "];
dcSEmpID= ds2.Tables["Salary"].Columns["EmpID "];

// Create the relationship between the two columns
DataRelation relEmpSal;
relEmpSal= new DataRelation("CustomerOrders", dcEEmpID, dcSEmpID);