Why does reflection return such a weird name for a lambda?

Question

I have this code:

class Program
{
    static void Main(string[] args)
    {
        Action whatToDo = () => {
            var member = (MemberInfo)(MethodBase.GetCurrentMethod());
            Thread.Sleep(0); //whatever, need something to put a breakpoint on
        };
        whatToDo();
    }
}

when I run it and use watch to look inside the object bound to member reference I see that MemberInfo.Name property has value <Main>b__0 .

This looks weird. Why wouldn't reflection make use of whatToDo name? What if I had more that one action with the same signature inside one member function - how would I tell which one is reported?

Why is such a weird name returned by reflection?

Answer 1

Lambda expressions which are being converted to delegates are transformed into methods. Your code is equivalent to:

class Program
{
    static void Main(string[] args)
    {
        Action whatToDo = MyLambda; // Method group conversion
        whatToDo();
    }

    static void MyLambda()
    {
        var member = (MemberInfo)(MethodBase.GetCurrentMethod());
        Thread.Sleep(0); //whatever, need something to put a breakpoint on
    }
}

... except that the compiler is smart enough to create new classes where necessary for captured variables etc. While in my transformation the extra method is called MyLambda , the C# compiler generates unspeakable names which aren't valid C# identifiers (to avoid collisions, prevent you from accessing them directly etc).