C＃、. net，委托，异步回调。 我在这里做错了什么？

Question

Heres a little class for a button in a menu in a game.

I'd like to be able to pass a delegate method _triggerMethod when I'm instantiating each button. Then that delegate method will get called when that button instances trigger method is called.

I'm trying out delegates in C# for the first time here. And as far as I'm interpreting the documentation here what I'm doing should work but visual studio is giving me a compile error in the Trigger method.

According to msdn article the code calling the delegate doesnt need to know about the original methods paramaters and such. What am I doing wrong? Also in the msdn article they are only typing "Del" and that does not work for me. I must type "Delegate" which is odd.

class MenuItem
    {
        private Rectangle clickArea;
        private string displayText;
        private Vector2 _position;
        private Delegate _triggerMethod;

        public MenuItem(Vector2 pos,string txt,Delegate trig)
        {
            displayText = txt;
            _position = pos;
            _triggerMethod = trig;
        }

        public void Draw(SpriteBatch sb)
        {
        }

        public void Select()
        {
        }

        public void DeSelect()
        {
        }

        public void IsMouseOnMe()
        {
        }

        public void Trigger()
        {
            _triggerMethod();
        }
    }

Answer 1

You haven't created any delegate definition.

Example (from the MSDN-page you linked):

public delegate void Del(string message);

Then, you need to use that as your Type:

    ** snip **
    private Del _triggerMethod;

    public MenuItem(Vector2 pos,string txt,Del trig)
    {
        displayText = txt;
        _position = pos;
        _triggerMethod = trig;
    }
    ** snip **

    public void Trigger()
    {
        _triggerMethod("some message");
    }

You can pass references of the delegate around without actually knowing what arguments it expects (since it's just a normal reference), but when you want to invoke it, you do need to give it the correct parameters.

Answer 2

You need to define the Del type if you want to use it:

public delegate void Del(string message);

public class MenuItem
{
    private Del _triggerMethod;
    public void Trigger()
    {
        _triggerMethod("Message");
    }
}

Note that you can use the built-in Action<string> delegate type instead of defining your own:

Action<string> _triggerMethod;
_triggerMethod("Message");

If you just use the Delegate type, you can invoke it using DynamicInvoke :

public void Trigger()
{
    _triggerMethod.DynamicInvoke();
}