SignalR, WebApi, Autofac, camelCasedJson - json

Question

I Have a web api app, inluding some SignalR functionality that has it's dependencies managed by Autofac.
SignalR, out of the box, does not support camelCased Json properties.
There's a decent fix here, but I need to integrate it with Autofac.
So.....
Here's the SignalR hub
public class PledgeHub : Hub
{
public void SendPledge(LivePledgeUpdate pledge)
{
Clients.All.sendPledge(pledge);
}
}
Here's the startup.cs class inluding the Camelcased Resolver from the article
[assembly: OwinStartup(typeof(Startup))]
namespace Filanthropy.Web
{
public partial class Startup
{
private readonly HttpConfiguration config;
public Startup()
{
config = new HttpConfiguration();
}
public void Configuration(IAppBuilder app)
{
// Set the dependency resolver to be Autofac.
var container = BuildContainer(config);
config.DependencyResolver = new AutofacWebApiDependencyResolver(container);
ConfigureAuth(app);
ConfigureWebApi(config);
app.MapSignalR();
app.UseWebApi(config);
app.UseAutofacMiddleware(container);
app.UseAutofacWebApi(config);
}
private void ConfigureWebApi(HttpConfiguration config)
{
config.MapHttpAttributeRoutes();
config.Routes.MapHttpRoute(
name: "DefaultApi",
routeTemplate: "api/{controller}/{id}",
defaults: new { id = RouteParameter.Optional }
);
var jsonFormatter = config.Formatters.OfType<JsonMediaTypeFormatter>().First();
jsonFormatter.SerializerSettings.ContractResolver = new CamelCasePropertyNamesContractResolver();
}
private static IContainer BuildContainer(HttpConfiguration config)
{
var builder = new ContainerBuilder();
// Register your Web API controllers.
builder.RegisterApiControllers(Assembly.GetExecutingAssembly());
// OPTIONAL: Register the Autofac filter provider.
builder.RegisterWebApiFilterProvider(config);
builder.RegisterType<PledgeHub>().ExternallyOwned();
GlobalHost.DependencyResolver.Register(typeof(JsonSerializer), () => JsonSerializerFactory.Value);
return builder.Build();
}
private static readonly Lazy<JsonSerializer> JsonSerializerFactory = new Lazy<JsonSerializer>(GetJsonSerializer);
private static JsonSerializer GetJsonSerializer()
{
return new JsonSerializer
{
ContractResolver = new FilteredCamelCasePropertyNamesContractResolver
{
TypesToInclude =
{
typeof(SignalRHubs.PledgeHub),
}
}
};
}
}
}
I get camelCased properties just fine with everything that's served via WebApi, but not via Signalr.

Answer 1

I'm guessing that your problem is this:
GlobalHost.DependencyResolver.Register(typeof(JsonSerializer), () => JsonSerializerFactory.Value);
If you're using Autofac as the container / dependency resolver, you want to register the serializer with Autofac, not with the soon-to-be-replaced global dependency resolver.
builder.Register(ctx => JsonSerializerFactory.Value).As<JsonSerializer>();
Also, I see you're using OWIN. When you use OWIN, you don't reference GlobalHost - you set up your hub configuration separately. The docs have an example showing how to do it:
public class Startup
{
public void Configuration(IAppBuilder app)
{
var builder = new ContainerBuilder();
// STANDARD SIGNALR SETUP:
// Get your HubConfiguration. In OWIN, you'll create one
// rather than using GlobalHost.
var config = new HubConfiguration();
// Register your SignalR hubs.
builder.RegisterHubs(Assembly.GetExecutingAssembly());
// Set the dependency resolver to be Autofac.
var container = builder.Build();
config.Resolver = new AutofacDependencyResolver(container);
// OWIN SIGNALR SETUP:
// Register the Autofac middleware FIRST, then the standard SignalR middleware.
app.UseAutofacMiddleware(container);
app.MapSignalR("/signalr", config);
}
}