Interfaces

gistfile1.cs

var anotherClass = new AnotherClass();
var worker = new Worker(anotherClass);
worker.DoWork();

class Worker
{
    private readonly WorkListener _listener;

    public Worker(WorkListener listener)
    {
        if (listener == null)
            throw new ArgumentNullException("listener");

        _listener = listener;
    }

    public void DoWork()
    {
        //..
        _listener.WorkDone();
    }
}

interface WorkListener
{
    void WorkDone();
}

class AnotherClass : WorkListener
{
    void WorkListener.WorkDone()
    {
        //..
    }
}