Delegate as parameter in C# class constructor

Question

Hi i have a class with a delegate as a parameter as shown in the code, but i get the errors Error 1 Type expected ...\\Classes\\Class1.cs 218 33 Classes and Error 2 ; expected ...\\Classes\\Class1.cs 218 96 Classes Error 2 ; expected ...\\Classes\\Class1.cs 218 96 Classes . How do i fix the issue? Thanks in advance! I'm trying to pass it byref so when a class initializes, some method of it is attached to the delegate.

public constructor(ref delegate bool delegatename(someparameters))
{
    some code
}

Answer 1

You cannot declare the delegate type in the constructor. You need to first declare the delegate type, and then you can use it in the constructor:

public delegate bool delegatename(someparameters);

public constructor(ref delegatename mydelegate)
{
   some code...
}

Answer 2

You can pass something like Action<T> ... not sure why you want to pass it by reference though. For example, you can have a method like this one:

static void Foo(int x, Action<int> f) {
    f(x + 23);
}

And call it like this:

int x = 7;
Foo(x, p => { Console.WriteLine(p); } );

Answer 3

1 - Why you're using the ref keyword?

2 - the constructor is the class name? if not, you're doing this wrong, different of PHP: public function __construct( .. ) { } the constructor is named of class name, for example:

class foo { 
   public foo() { } // <- class constructor 
}

3 - Normally the types of delegates are void.

You're looking for this?

 class Foo {

        public delegate bool del(string foo);

        public Foo(del func) { //class constructor
                int i = 0;
                while(i != 10) {
                        func(i.ToString());
                        i++;
                }
        }
    }

Then:

class App
{

    static void Main(string[] args)
    {

        Foo foo = new Foo(delegate(string n) {
                            Console.WriteLine(n);
                            return true; //this is it unnecessary, you can use the `void` type instead.          });
        Console.ReadLine();
    }
}

The output:

1
2
3
4
5
6
7
8
9