Use a DataAdapter to fill a DataTable : DataAdapter « ADO.Net « C# / CSharp Tutorial

1. C# / CSharp Tutorial
2. ADO.Net
3. DataAdapter

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

    class Program
    {
        static void Main(string[] args)
        {
            string sqlConnectString = "Data Source=(local);Integrated security=SSPI;Initial Catalog=AdventureWorks;";
            string sqlSelect = "SELECT TOP 5 * FROM Sales.SalesOrderDetail";

            SqlDataAdapter da = new SqlDataAdapter(sqlSelect, sqlConnectString);
            DataTable dt = new DataTable();
            da.Fill(dt);

            
            dt.Columns.Add(new DataColumn("ExtendedPrice", typeof(Decimal),
                "UnitPrice * (1 - UnitPriceDiscount) * OrderQty"));

            foreach (DataRow row in dt.Rows)
                Console.WriteLine("ID = {0}, UnitPrice = {1}, " +
                    "Disc = {2}, Qty = {3}, Total = {4}",
                    row["SalesOrderDetailID"], row["UnitPrice"],
                    row["UnitPriceDiscount"], row["OrderQty"],
                    row["ExtendedPrice"]);
        }
    }