event C# with Example

An event allows the developer to implement a notification pattern. 
Simple example 
public class Server 
{ 
// defines the event 
public event EventHandler DataChangeEvent; 
void RaiseEvent() 
{ 
var ev = DataChangeEvent; 
if(ev != null) 
{ 
ev(this, EventArgs.Empty); 
} 
 

} 
} 
public class Client 
{ 
public void Client(Server server) 
{ 
// client subscribes to the server's DataChangeEvent 
server.DataChangeEvent += server_DataChanged; 
} 
private void server_DataChanged(object sender, EventArgs args) 
{ 
// notified when the server raises the DataChangeEvent 
} 
} 
MSDN reference