Creating and Manipulating DataSets

using System;
using System.Data;
using System.Data.SqlClient;

namespace LearningDataSets
{
    class RelationsExample
    {
        static void Main(string[] args)
        {
            //Queries
            string sql1 = "select * from customers";
            string sql2 = "select * from orders";
            string connstring = "Server=localhost;Database=Northwind;UID=sa;Password=;";

            //Fill DataSet
            DataSet ds = new DataSet();
            SqlDataAdapter da = new SqlDataAdapter(sql1, connstring);
            da.Fill(ds, "Customers");
            da.SelectCommand.CommandText = sql2;
            da.Fill(ds, "Orders");

            //Establish Relation
            ds.Relations.Add("CustomerOrderRelation",
                ds.Tables["Customers"].Columns["CustomerID"],
                ds.Tables["Orders"].Columns["CustomerID"]);
        }
    }
}