How can I create a dynamic method to handle an event?

Question

In C#, how can I create a dynamic method that can be used to handle an event?

Here is an event:

public event EventHandler<EventArgs> refresh;

Here is a method:

public void Test()
{

}

How can I dynamically create a method to handle the refresh event, such that the dynamic method calls the Test method?

The Test method above is an example of a method to be called.

Why can't you just subscribe to that event and call the Test method from there? — Kinetic, Jul 01 '16 at 03:05
The code is for users to subscribe to events at runtime. The above method to call is just an example. — Simon, Jul 01 '16 at 03:13
So "refresh" is an event from a class and Test is a method that is not part of that class? — Kinetic, Jul 01 '16 at 03:18
Yes. "Test" can be in any class. The object that has the "Test" method is already instantiated. — Simon, Jul 01 '16 at 03:22
Anyway, you could take a look at this answer to a similar question : http://stackoverflow.com/a/45901/6347013 — Kinetic, Jul 01 '16 at 03:43
Can you please provide more examples of the methods that your would like dynamically called? — Enigmativity, Jul 01 '16 at 04:22

score 0 · Answer 1 · answered Jul 01 '16 at 03:33

0

Well, you could simply subscribe to the event.

public class SomeClass
{
    public event EventHandler<EventArgs> refresh;
}

public void Test()
{
}

void Main()
{
    var some = new SomeClass();
    some.refresh += (sender, e) => Test();
    // or
    some.refresh += Refreshed;
}

void Refreshed(object sender, EventArgs e)
{
    Test();
}

answered Jul 01 '16 at 03:33

Kinetic

2,640
17
35

This is what I am wanting to do, but I am in need of help on how to create the "Refreshed" method dynamically. – Simon Jul 01 '16 at 03:37
Can't you tell us why it need to be created dynamically? – Kinetic Jul 01 '16 at 03:40
The "Test' method is an example of a method than can be called. A user can choose any method to be called. As such, it has to be created dynamically. – Simon Jul 01 '16 at 03:43
4

I guess that's the kind of information I would write in a question. – Kinetic Jul 01 '16 at 03:44
1

@user3736648 if "A user can choose any method to be called" ie. a drop down list, you could drop all subscribed events ([See here for some pre-baked code](https://stackoverflow.com/questions/91778/how-to-remove-all-event-handlers-from-a-control)), then subscribe to the selected method `some.refresh += (sender, e) => ChoosenMethod();`. Is this what you mean by dynamic? – Bennett Yeo Jul 01 '16 at 03:57

score 0 · Answer 2 · answered Jul 01 '16 at 14:52

If the method you want to invoke is an instance method in some class and you have an instance of that class and the name of the method, you can use Delegate.CreateDelegate() to create a delegate to that method and then use a lambda to invoke it in an event handler:

static EventHandler<EventArgs> CreateHandler(object methodObject, string methodName)
{
    var methodDelegate =
        (Action)Delegate.CreateDelegate(typeof(Action), methodObject, methodName);

    return (s, e) => methodDelegate();
}

Usage can then look like this (assuming Test is in class C):

refresh += CreateHandler(new C(), "Test");

refresh(this, EventArgs.Empty);

@downvoter What do you think is wrong with this answer? – svick Jul 01 '16 at 17:42 — svick, Jul 01 '16 at 17:42

How can I create a dynamic method to handle an event?

2 Answers2