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?

Answer 1

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.