CODEWITHSUNDEEP
c#eventsreflection
Fabian
Fabian

Reputation: 63

Add Event Handler using Reflection ? / Get object of type?

how to add a event handler myhandler using reflection if I only have the type AType of the event thrower?

Delegate myhandler = SomeHandler;

EventInfo info= AType.GetEvent("CollectionChanged");

info.AddEventHandler( ObjectOfAType, myhandler )

Upvotes: 1

Views: 1656

Answers (1)

Marc Gravell
Marc Gravell

Reputation: 1062770

Basically, what you have is fine. The only glitch is that myhandler actually needs to be of the correct type, which is to say: of the type defined by the event.

For example:

using System;
using System.Collections.Specialized;
using System.Reflection;

class Program
{
    static void Main()
    {
        Type AType = typeof(Foo);
        var ObjectOfAType = new Foo();

        Delegate myhandler = (NotifyCollectionChangedEventHandler)SomeHandler;
        EventInfo info = AType.GetEvent("CollectionChanged");
        info.AddEventHandler(ObjectOfAType, myhandler);

        // prove it works
        ObjectOfAType.OnCollectionChanged();
    }

    private static void SomeHandler(object sender, NotifyCollectionChangedEventArgs e)
        => Console.WriteLine("Handler invoked");
}
public class Foo
{
    public void OnCollectionChanged() => CollectionChanged?.Invoke(this, null);
    public event NotifyCollectionChangedEventHandler CollectionChanged;
}

There is a Delegate.CreateDelegate() method that takes a delegate type, an object instance, and a MethodInfo method; you can use this (using the event-type from EventInfo info) to create an appropriate delegate instance for a given method on a particular object.

Upvotes: 1

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