// Form1.cs, aus MyComponentDemo
using System;
using System.ComponentModel;
using System.Threading;
using System.Windows.Forms;

namespace MyComponent
{
  public class Notifier: Component, INotifier
  {
    private string notifyText = "unbekannt";
    
    public void Notify(string text)
    {
      this.notifyText = text;
      SimuliereBerechnung(4);
    }

    private void SimuliereBerechnung(int seconds)
    {
      Form.ActiveForm.Cursor = Cursors.WaitCursor;
      DateTime end = DateTime.Now.AddSeconds((double)seconds);
      while (DateTime.Now < end)
      {
        Thread.Sleep(100); Application.DoEvents();
      }
      Form.ActiveForm.Cursor = Cursors.Default;
      BerechnungFertig(this, new NotifyEventArgs(notifyText));
    }

    public event NotifyEventHandler BerechnungFertig;
    public delegate void NotifyEventHandler(object sender, NotifyEventArgs e);
    public class NotifyEventArgs : EventArgs
    {
      public NotifyEventArgs(string notifyText)
      {
        this.notifyMessage = notifyText;
      }

      string notifyMessage;
      public string NotifyMessage
      {
        get { return notifyMessage; }
        set { notifyMessage = value; }
      }
    }
  }
}


// INotifier.cs, aus Projekt MyComponent 
using System;
namespace MyComponent
{
  public interface INotifier
  {
    event Notifier.NotifyEventHandler BerechnungFertig;
    void Notify(string text);
  }
}




// Notifier.cs, aus Projekt MyComponent
using System;
using System.Windows.Forms;
using MyComponent;

namespace MyComponentDemo
{
  public partial class Form1 : Form
  {
    INotifier iNotifier;
    
    public Form1()
    {
      InitializeComponent();
      iNotifier = (INotifier)notifier1;
      iNotifier.BerechnungFertig += new Notifier.NotifyEventHandler(iNotifier_BerechnungFertig);
    }

    void iNotifier_BerechnungFertig(object sender, Notifier.NotifyEventArgs e)
    {
      MessageBox.Show("Die Berechnung in Komponente notifier1 ist fertig.\r\n"+
        "Der Benachrichtigungstext war:" + e.NotifyMessage);
    }

    private void btnStart_Click(object sender, EventArgs e)
    {
      iNotifier.Notify("Hallo Welt!");
    }
  }
}