using System.Data.SQLClient;


SQLConnection con=new SQLConnection("Your connection string");

SQLDataAdapter ad1;
SQLDataAdapter ad2;

DataSet ds=new DataSet();
DataRelation dr;

private void button1_click(object sender,EventArgs e)
{
  ad1=new SQLDataAdapter("Select * from dept",con);
  ad2=new SQLDataAdapter("select * from emp",con);
  ad1.Fill(ds'"d");
  ad2.Fill(ds,"e";
  DataColumn pk=ds.Tables["d"].Columns["deptno"];
  DataColumn fk=ds.Tables["e"].Columns["deptno"];
  dr=new DataRelation("rel",pk,fk);
  ds.Relations.Add(dr);
  DataGrid1.DataSource=ds;
  
}