public class SampleEventArgs
{
    public SampleEventArgs(string s) { Text = s; }
    public String Text {get; private set;} // readonly
}
public class Publisher
{
    // Declare the delegate (if using non-generic pattern).
    public delegate void SampleEventHandler(object sender, SampleEventArgs e);

    // Declare the event.
    public event SampleEventHandler SampleEvent;

    // Wrap the event in a protected virtual method
    // to enable derived classes to raise the event.
    protected virtual void RaiseSampleEvent()
    {
        // Raise the event by using the () operator.
        SampleEvent(this, new SampleEventArgs("Hello"));
    }
}