Question

I am writing a C# class to wrap around a simple web service. The RESTful stuff was easy to wrap up, but now I need to raise an event when something on the server changes.

I’ve set the server up to make an event stream available, but I don’t know how to pick up the stream in C#.

Currently I’m dong something like this:

public class ServiceWrapper
{
    private readonly wc = new WebClient();

    public ServiceWrapper()
    {
        wc.OpenReadAsync(new Uri(UriOfEvent));
        wc.OpenReadCompleted += ServerEventOccurs;
    }

    private void ServerEventOccurs(object sender, OpenReadCompletedEventArgs args)
    {
        using (var sr = new StreamReader(args.Result))
        {
            var message = ParseStream(sr);
            RaiseServerEventOccurred(message);
        }

        wc.OpenReadAsync(new Uri(UriOfEvent));
    } 

    //usual code for declaring and raising ServerEventOccurred event
}

In my test the event gets picked up once, but not twice. The event on the server is essentially a switch – something happens and it goes on, something else happens and it goes off. I know the switching works, because I’ve hooked the event stream up to a normal web page to test it.

How should I be dealing with event streams in C#?

Edit 1: I’ve updated the code to fix the bug TimVK points out, but the event stream still isn’t being picked up the second time it should be.

Answer 1

Doesn’t it work when you put your wc as a property in the class instead of creating always a new one in your methods?

public class ServiceWrapper 
{ 
    WebClient wc {get;set;}
    public ServiceWrapper() 
    { 
        wc = new WebClient(); 
        wc.OpenReadAsync(new Uri(UriOfEvent)); 
        wc.OpenReadCompleted += ServerEventOccurs; 
    } 
 
    private void ServerEventOccurs(object sender, OpenReadCompletedEventArgs args) 
    { 
        using (var sr = new StreamReader(args.Result)) 
        { 
            var message = ParseStream(sr); 
            RaiseServerEventOccurred(message); 
        } 
 
        wc = new WebClient(); 
        wc.OpenReadAsync(new Uri(UriOfEvent)); 
    }  
 
    //usual code for declaring and raising ServerEventOccurred event 
} 

Then I suppose the event should be raised everytime.