Simple Delegate and Event Implementation Sample

class definition:

public class DelegateAndEvent
{
 //it is a good practice to name your delegates with "EventHandler"
 public delegate void ErrorEventHandler(DelegateAndEvent sender, ErrorEventArgs args);

 //declare event
 public event ErrorEventHandler ErrorRaised;

 //a better way of returning values is to create a class which inherits the EventArgs class and add the
 //desired property(ies)
 public class ErrorEventArgs : EventArgs
 {
     private string _errmsg;
     public string ErrorMessage
     {
         get { return _errmsg; }
         set { _errmsg = value; }
     }

     public ErrorEventArgs() { }
     public ErrorEventArgs(string error)
     {
         _errmsg = error;
     }
 }

 /// Method to allow raising of error (can either be public or private)
 public void RaiseError(string error)
 {
     if (!string.IsNullOrEmpty(error))
     {
         //check is event is not null (event has a subscriber)
         if (ErrorRaised != null)
         {
             ErrorRaised(this, new ErrorEventArgs(error));
         }
     }

 }
}


code behind:


public partial class _Default : System.Web.UI.Page
{
 DelegateAndEvent dne = new DelegateAndEvent();

 protected override void OnInit(EventArgs e)
 {
     base.OnInit(e);
     dne.ErrorRaised += new DelegateAndEvent.ErrorEventHandler(dne_ErrorRaised);
 }

 protected void Page_Load(object sender, EventArgs e)
 {
 }

 protected void btnEvent_Click(object sender, EventArgs e)
 {
     dne.RaiseError("Error was forced to be raised!");

 }

 void dne_ErrorRaised(DelegateAndEvent sender, DelegateAndEvent.ErrorEventArgs args)
 {
     lblError.Text = args.ErrorMessage;
 }
}

Simple Delegate and Event Implementation Sample