Expression-bodied function members efficiency and performance in C# 6.0

Question

In a new C# 6.0 we can define methods and properties using lambda expressions.

For instance this property

public string Name { get { return First + " " + Last; } } 

can be now defined as follows:

public string Name => First + " " + Last;  

The information about expression-boided function members you can find here: http://blogs.msdn.com/b/csharpfaq/archive/2014/11/20/new-features-in-c-6.aspx

Does anyone know if there's any overhead when using new syntax? Can it slow down (or improve efficiency of) the application or maybe it doesn't matter?

Answer 1

In a new C# 6.0 we can define methods and properties using lambda expressions.

No, you can't. You can define method and property bodies using syntax which looks like a lambda expression, in that it uses the token =>.

However, importantly this does not mean that there's a delegate type involved. (Whereas a lambda expression is only permitted in a context where it's converted to an expression tree or delegate type.)

This is purely syntactic sugar. Your two example code snippets will compile to the exact same IL. It's just a different way of representing the body of a property getter or method.

Answer 2

They will compile down to the same IL, you can always test this yourself by doing it and using ildasm to extract the IL.