Question

Both snippets below product the same output.
I understand how Func encapsulates a method with a single parameter, and returns a bool value. And you can either assign it a
method, anonymous method or a lambda expression.

Func<int, bool> deleg = i => i < 5;
Console.WriteLine("deleg(4) = {0}", deleg(4));

Below is using expression trees which I don’t fully understand yet. Why would I want to do it this way? Is it more flexible, what advantage does it give me?

System.Linq.Expressions.Expression<Func<int, bool>> expr = i => i < 5;
Func<int, bool> deleg2 = expr.Compile();
Console.WriteLine("deleg2(4) = {0}", deleg2(4));

Answer 1

Basically, the Expression tree is the body of a lambda expression, that allows you to

• introspect the expression (see what’s in it so to say)
• manipulate the expression (simplify, extend (e.g. add new functionality or modify to work on different items).

Once you Compile() the expression, it is just another delegate, which you can only call, not inspect or modify.

Whenever you want to

• create expressions dynamically (I mean: construct, not allocate)
• operate on expressions dynamically

the Function<> types are not sufficient.