Coding in C # I ended up making a mistake, maybe because of familiarity with other languages I usually work with, and I forgot the parentheses.
string.Concat(numero.ToString, "A")
I received the following error:
can not convert from 'method group' to 'object'
I've even been researching what this method group is, but since it's a concept I've never seen in another language I did not fully understand its purpose, or why it exists.
I do not know if you already understand that the methods have overloads ( signatures ) then as there are several methods with the same name, they form a group. Obviously the group can be formed by only one method if it has only one signature.
This was a very interesting idea originally designed to make it easier to use delegates, and consequently of events , so any of the methods can be associated with the delegate directly. Then lambdas have benefited as well.
If the method parameter Concat() hypothetically expected a delegate, then it would work. Of course that would not make sense.
ToString() is a method, ToString is a method group, so they are two very distinct things. It has language that is just a simplification of syntax because this new concept does not exist.
Everywhere I accept a delegate you can create it in several ways:
Action<string> x = delegate(string txt) { WriteLine(txt); };
This is the initial form of C # and is almost obsolete, replaced by:
Action<string> x = txt => WriteLine(txt);
Or you can use a method group :
Action<string> x = WriteLine;
According to the delegate's signature the referenced method, in this case the WriteLine() , with the equivalent signature will be called.
Using a delegate reference:
using System;
using static System.Console;
public class Program {
public static void Main() {
var numero = 123;
Func<string, string> func = numero.ToString;
WriteLine(func("000000"));
Func<string> func2 = numero.ToString;
WriteLine(func2());
Action<string> a = delegate(string txt) { WriteLine(txt); };
Action<string> b = txt => WriteLine(txt);
Action<string> c = WriteLine;
a("abc");
b("abc");
c("abc");
}
}
See running on .NET Fiddle . And No Coding Ground . Also I put it in GitHub for future reference .
If you are curious about reading the language specification , you have detailed information on how it works, this chapter is a short text: P