I'm finally getting time to dig into C# in Depth and try some stuff out. It's pleasing to see some of the terse constructs we now have.As a small example, this is great:

public decimal TotalPrice
{
     get
     {
         return 
            Lines.Sum(l => l.Price * l.Quantity * (IsVat ? 1.175m : 1) );
     }
}