SignalR, Owin and exception handling

Question

I\'ve developed a sample SignalR application based on ASP.NET 4.5 & Owin, and I\'ve hosted that app on IIS 7.5.

Everything is working fine, but how can I handle

Answer 1

The answer by @halter73 is great for errors thrown inside hubs, but it doesn't catch errors thrown during their creation.

I was getting the exception:

System.InvalidOperationException: 'foobarhub' Hub could not be resolved.

The server was returning an HTML page for this exception, but I needed it in JSON format for better integration with my Angular app, so based on this answer I implemented an OwinMiddleware to catch exceptions and change the output format. You could use this for logging errors instead.

public class GlobalExceptionMiddleware : OwinMiddleware
{
    public GlobalExceptionMiddleware(OwinMiddleware next)
        : base(next)
    {
    }

    public override async Task Invoke(IOwinContext context)
    {
        try
        {
            await Next.Invoke(context);
        }
        catch (Exception ex)
        {
            context.Response.ContentType = "application/json";
            context.Response.StatusCode = 500;

            await context.Response.WriteAsync(JsonConvert.SerializeObject(ex));
        }
    }

}

Add the registration in OwinStartup.cs, just remember to place it before the MapSignalR method call:

public class OwinStartup
{
    public void Configuration(IAppBuilder app)
    {
        app.Use(); // must come before MapSignalR()

        app.MapSignalR();
    }
}