public class KlasseB
{
  public event EventHandler EventVonB;

  public void DoSomething()
  {
    OnEventVonB();
  }

  protected virtual void OnEventVonB()
  {
    EventHandler tmp = EventVonB;
    if (tmp != null)
    {
      tmp(this, new EventArgs());
    }
  }
}

public class KlasseA
{
  private KlasseB klasseB;

  public event EventHandler EventVonA
  {
    add { this.klasseB.EventVonB += value; }
    remove { this.klasseB.EventVonB -= value; }
  }

  public KlasseA()
  {
    this.klasseB = new KlasseB();
  }

  public void DoSomethingWithB()
  {
    this.klasseB.DoSomething();
  }
}

class KlasseA
{
     private KlasseB _klasseB = new _klasseB();

     public event EventHandler SomeEvent;

     public KlasseA()
     {
         this._klasseB.SomeEvent += new EventHandler(SomeHandler);
     }

     private void SomeHandler(Object sender, EventArgs e)
     {
             if(SomeEvent != null)
                  SomeEvent(this, e);
     }
}

class KlasseB
{
     private KlasseC _klasseC = new _klasseC();

     public event EventHandler SomeEvent;

     public KlasseB()
     {
         this._klasseC.SomeEvent += new EventHandler(SomeHandler);
     }

     private void SomeHandler(Object sender, EventArgs e)
     {
             if(SomeEvent != null)
                  SomeEvent(this, e);
     }
}

class KlasseC
{
     public event EventHandler SomeEvent;

     public SomeMethod()
     {
           // some code

          if(SomeEvent != null)
               SomeEvent(this, EventArgs.Empty);
     }

}