Java Observer / Observable equivalent in C#?

Question

I'm toying a bit with IObservable and IObserver in C# after using it's Java equivalent. However I'm not entirely sure how to use it correctly. I've Googled this, but the results are either too problem-specific or way too unnecessarily complex.

This is my very basic Java code :

public class SomeController extends Observable{

    public void doSomething()
    {
        //dostuff
        setChanged();
        notifyObservers();
    }

}

public class SomeView implements Observer{

    private SomeController controller;

    public SomeView (SomeController ctrl)
    {
        this.controller= ctrl;
        ctrl.addObserver(this);
    }

    public void update (Observable o,Object arg)
    {
        if (o==controller)
        System.out.println("Update detected");
    }

}

Right, so how do I do the very exact same thing in C#?

Chris Mantle · Accepted Answer · 2013-12-11T11:42:11.647

C# has built-in support for the observer pattern, in the form of events. I think this is what you're looking for.

public delegate void UpdatedEventHandler(object sender, EventArgs e);

public class SomeController {

    public event UpdatedEventHandler Updated;

    protected virtual void OnUpdated(EventArgs e) 
    {
        if (Updated != null)
        {
            this.Updated(this, e);
        }
    }

    public void DoSomething()
    {
        // Do stuff

        this.OnUpdated(new EventArgs());
    }
}

public class SomeView implements Observer{

    private SomeController controller;

    public SomeView(SomeController ctrl)
    {
        this.controller = ctrl;
        ctrl.Changed += this.OnControllerChanged;
    }

    private void OnControllerChanged(object sender, EventArgs e)
    {
        if (sender == this.controller)
        {
            Console.WriteLine("Update detected");
        }
    }
}

In C#, IObservable and IObserver primarily appear as part of Reactive Extensions (Rx), to represent asynchronous observable sequences and event listeners.

Thanks. This seems to be doing what I want it to. – Cata Visan Dec 11 '13 at 12:01 — Cata Visan, Dec 11 '13 at 12:01

score 0 · Answer 2 · answered Dec 11 '13 at 11:31

0

C# has events a delegates.

Check out http://blog.monstuff.com/archives/000040.html

But as Observable is just an interface you could make a replica of the java-way if you want.

answered Dec 11 '13 at 11:31

The eternal newbie

131
9

score 0 · Answer 3 · edited May 23 '17 at 12:03

0

Are you talking about INotifyPropertyChanged implementation?
Here's an exemple : INotifyPropertyChanged exemple
In this case, you should probably use MVVM patern instead of MVC : Mvvm post
Hope this helps

edited May 23 '17 at 12:03

Community

1
1

answered Dec 11 '13 at 11:36

anthoLB29

105
1
9

Java Observer / Observable equivalent in C#?

3 Answers3