Issue raising a simple event

Question

My interface has an event that don't has an arguments

public interface IMyInterface
{
     event EventHandler OnSomethingHappened;
}

Here is how I am implementing it.

   public class MyBaseClass : IMyInterface
    {
private event EventHandler onSomethingHappened;
public event EventHandler OnSomethingHappened
{
    add
    {
        onSomethingHappened-= value;
        onSomethingHappened+= value;
    }

    remove
    {
        onSomethingHappened-= value;
    }
}
    }

But somehwere else when I try to use it as follows

if ( MyBaseClassInstance.OnSomethingHappened != null )
        MyBaseClassInstance.OnSomethingHappened();

I get following compilation error

The event 'ConsoleApplication1.IMyInterface.OnSomethingHappened' can only appear on the left hand side of += or -=

What am I doing wrong?

`MyBaseClass` is **not** implementing `IMyInterface`. Regarding error, search for it, e.g. [here](http://stackoverflow.com/q/4496799/1997232) is same problem. — Sinatr, Feb 11 '15 at 16:15
thakns I tried doing that but continue to get same error. Updated my question for changes I made — paul deter, Feb 11 '15 at 16:24

Andrei Lujan · Accepted Answer · 2015-02-11T16:41:25.360

This is how your code might look:

    public interface IMyInterface
    {
        event EventHandler OnSomethingHappened;
    }

    //implement the interface
    public class MyBaseClass : IMyInterface
    {
        public event EventHandler OnSomethingHappened;

        public void DoSomeLogicWhichRaisesTheEvent()
        {
            if (OnSomethingHappened != null)
            {
                MyBaseClass sender = this;
                var eventArgs = new EventArgs();
                //let all subscibers to event know that the event happened
                OnSomethingHappened(sender, eventArgs);
            }
        }
    }

    public class ConsumerClass
    {
        private IMyInterface myBaseClassInstance;

        public ConsumerClass()
        {
            myBaseClassInstance = new MyBaseClass();
            //attach to the event
            myBaseClassInstance.OnSomethingHappened += MyBaseClassInstance_OnSomethingHappened;
        }

        private void MyBaseClassInstance_OnSomethingHappened(object sender, EventArgs e)
        {
            //react to the raised event
            throw new NotImplementedException();
        }
    }

As you can see you need to implement the IMyInterface interface, and when MyBaseClass needs to raise the event you call OnSomethingHappened(sender, eventArgs);

ConsumerClass is where you need to consume, or to do something, as a reaction to the raised event. You may consider to rename MyBaseClass to some other name, without 'Base' in it, because it is not an abstract class.

Could you explain briefly what's happening in this code and how that solves the problem? — anaximander, Feb 11 '15 at 16:34

Issue raising a simple event

1 Answers1