如果使用委托，我需要那些方法是静态的吗？

Question

I have a C# code like this:

using System;
delegate int anto(int x);
class Anto 
{
    static void Main()
    {
        anto a = square;
        int result = a(3);
        Console.WriteLine(result);
    }
    static int square(int x)
    {
        return x*x;
    }
}

which output's : 9 . Well I'm a novice in C#, so I started to play around with this code and so when I remove the static keyword from the square method, then I'm getting error like this:

An object reference is required to access non-static member `Anto.square(int)'
Compilation failed: 1 error(s), 0 warnings

what causes this error? So if I use delegates I need the method to be static ?

I run this code here

Thanks in advance.

Answer 1

Because Main is static, it can only reference other static members. If you remove static from square , it becomes an instance member, and in the static context of Main , there is no instance of any object, so instance members aren't 'valid'.

Thankfully there's nothing crazy going on with delegates, it's just the way static works - it indicates members are global to a type and not an instance of that type.

Answer 2

It's required to be static because it's used in a static method. You'd need an instance of Anto to make your example work.

var myAnto = new Anto();
anto a = myAnto.square;

This is untested and may not compile based on the protection level of Anto.square .

Answer 3

It doesn't need to be static. You can assign a non-static method to a delegate, but if it is non-static then you need to instatiate an object of type Anto :

Anto anto = new Anto();
anto a = anto.square;

It's rather pointless here though since the method doesn't access any of the instance members. It makes more sense that it is static.

Answer 4

Static methods may be called from before creating an instance, you must be a static method.

Can be written as follows, if necessary

anto a = (x)=>x*x ;