It's possible to create an expression tree, if you declare it as such.

But is it possible to get an expression tree for an ordinary chunk of code such as a method or property getter?

What I'm trying to do is, let's say for an order processing system, I have a class for order items:

class Item : Entity
{
    [Cascade]
    public Document document { get; set; }
    public int line { get; set; }

    public Product product { get; set; }
    public string description { get; set; }
    public decimal qty { get; set; }
    public decimal price { get; set; }
    public decimal net
    {
        get
        {
            return qty * price;
        }
    }
    public VatCode vat_code { get; set; }
}

where the net value equals qty * price, so I'd like to declare it as such, either with a property or method, and then also have the framework introspect that expression so it can generate appropriate SQL for defining a corresponding calculated column in a corresponding database view.

The most obvious way to do this would be to get the expression tree for a property getter or a method, but I can't find any indication how to do this, or that it is possible. (I have found a way to get a method body as a byte stream, but that's not what's desired here.)

If that isn't possible, I suppose the recommended solution would be to declare something like a static field that is an expression tree, and compile/run it at run time for internal use, and also introspect as normal for SQL generation?