using System;

using System.Data;

using System.Xml;

public class Program

{

    public static void Main()

    {

        var table = new DataTable();

        table.Columns.Add( "Id", typeof(Int32) );

        table.Columns.Add( "Code", typeof(String) );

        table.Columns.Add( "Description", typeof(string) );

        table.Columns.Add( "Quantity", typeof(Int32) );

        table.Columns.Add( "ItemPrice", typeof(decimal) );

        table.Columns.Add( "SubTotal", typeof( decimal ), "Quantity*ItemPrice");

        table.Columns.Add( "Taxes", typeof( decimal ), "SubTotal*0.21");

        table.Columns.Add( "LineTotal", typeof( decimal ), "SubTotal + Taxes");

        table.Rows.Add( 1, "DECA10", "Coffee decafinated", 1, 2.5 );

        table.Rows.Add( 2, "ESPR", "Espresso", 2, 2.5 );

        string subTotal = ((decimal)table.Compute( "Sum(SubTotal)", "")).ToString("N2");

        string total = ((decimal)table.Compute( "Sum(LineTotal)", "")).ToString("N2");

        string taxTotal = ((decimal)table.Compute( "Sum(Taxes)", "")).ToString("N2");

        string quantityTotal = table.Compute( "Sum(Quantity)", "").ToString();

        Console.WriteLine( "Sub total  = {0} €", subTotal );

        Console.WriteLine( "Taxes      = {0} €", taxTotal );

        Console.WriteLine( "Total      = {0} €", total );

        Console.WriteLine( "Quantity   = {0} pieces", quantityTotal );

    }

}