C# 4 and .NET 4

emoting and events ❘ OC227
The method that will be implemented in the client has some strict requirements. It can only have input
parameters — return types, ref, and out parameters are not allowed — and the argument types must be
either [Serializable] or remotable (derived from MarshalByRefObject). These requirements are fulfilled
by the parameters that are defined with the EventHandler delegate.
Within the RemoteObject class, declare an event name Status of type EventHandler.
The client must add an event handler to the Status event to receive status information from the remote object:
public class RemoteObject : MarshalByRefObject
{
public RemoteObject()
{
Console.WriteLine("RemoteObject constructor called");
}
public event EventHandler Status;
code snippet RemotingAndEvents/RemoteObject/RemoteObject.cs
The LongWorking() method checks whether an event handler is registered before the event is fired by
calling Status(this, e). To verify that the event is fired asynchronously, fire an event at the start of the
method before doing the Thread.Sleep() and after the sleep:
public void LongWorking(int ms)
{
Console.WriteLine("RemoteObject: LongWorking() Started");
StatusEventArgs e = new StatusEventArgs(
"Message for Client: LongWorking() Started");
// fire event
if (Status != null)
{
Console.WriteLine("RemoteObject: Firing Starting Event");
Status(this, e);
}
System.Threading.Thread.Sleep(ms);
e.Message = "Message for Client: LongWorking() Ending";
// fire ending event
if (Status != null)
{
Console.WriteLine("RemoteObject: Firing Ending Event");
Status(this, e);
}
Console.WriteLine("RemoteObject: LongWorking() Ending");
}
event arguments
As you’ve seen in the RemoteObject class, the class StatusEventArgs is used as an argument for the
delegate. With the Serializable attribute an instance of this class can be transferred from the server to
the client. Here is a simple property of type string to send a message to the client:
[Serializable]
public class StatusEventArgs : EventArgs
{
public StatusEventArgs(string message)
{
this.Message = message;
}
public string Message { get; set; }
}
code snippet RemotingAndEvents/RemoteObject/RemoteObject.cs
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