Adding some filters to hub methods (like AcctionFilters in MVC)

Question

Is there anyway to define and add method filters for hub functions (like ActionFilters in mvc) I mean something like this :

public class MyHub : Hub 
{

    [Log]
    public string RegisterUser(UserModel model){
        ...
    }
}

where I can do some control inside the LogAttribute implementation.

Answer 1

You should be able to achieve similar functionality to action filters in ASP.NET MVC by using SignalR's Hub pipeline:

public class LoggingPipelineModule : HubPipelineModule 
{ 
    protected override bool OnBeforeIncoming(IHubIncomingInvokerContext context) 
    {
        Debug.WriteLine("Invoking '{0}.{1}({2})'.",
            context.MethodDescriptor.Hub.Name,
            context.MethodDescriptor.Name,
            string.Join(", ", context.Args));

        return base.OnBeforeIncoming(context); 
    }

    protected override object OnAfterIncoming(object result, IHubIncomingInvokerContext context)
    {
        Debug.WriteLine("Finished Invoking '{0}.{1}'. Returned '{2}'.",
            context.MethodDescriptor.Hub.Name,
            context.MethodDescriptor.Name,
            result);

        return base.OnAfterIncoming(result, context); 
    }
}

If you only want to log for methods with a custom attribute attached, you can check for your custom attribute before logging:

protected override bool OnBeforeIncoming(IHubIncomingInvokerContext context) 
{
    if (context.MethodDescriptor.Attributes.OfType<MyAttribute>().Any())
    {
        // Log here.
    }

    return base.OnBeforeIncoming(context); 
}

You can register your module before your call to MapSignalR:

public void Configuration(IAppBuilder app) 
{ 
    GlobalHost.HubPipeline.AddModule(new LoggingPipelineModule()); 
    app.MapSignalR();
}