OWIN Startup Class

Question

Can someone please tell me the exact role of the OWIN startup class. Basically what I am looking for :

• Whats its purpose
• When is it called, it is just once or per request
• Is this a good place to configure my Dependency Injection library.

Answer 1

Owin is designed to be pluggable deisgn. there are a set of services which you can change/replace from the configuration. For example in the following configuration, i have

• enabled webapi
• Enabled Signalr
• Enabled Attribute Based routing for Signalr
• Configured default Dependency Resolver
• Replaced Logging service with custom logger

So , this way, you can configure the complete configuration. It will be called only once at startup. You can set/use dependency resolver and configure it here, but that depends mainly on your overall design.

public class OwinStartup
{
    //initialize owin startup class and do other stuff
    public void Configuration(IAppBuilder app)
    {
        app.UseWelcomePage("/");
        //var container = new UnityContainer();

        HttpConfiguration httpConfiguration = new HttpConfiguration();
        httpConfiguration.Routes.MapHttpRoute(
            name: "MyDefaultApi",
            routeTemplate: "api/v2/{controller}/{id}",
            defaults: new { id = RouteParameter.Optional }
            );

        //Maps the attribute based routing
        httpConfiguration.MapHttpAttributeRoutes();

        //Set the unity container as the default dependency resolver
        httpConfiguration.DependencyResolver = new UnityWebApiDependencyResolver(new UnityContainer());

        //replace (or add) the exception logger service to custom Logging service
        httpConfiguration.Services.Replace(typeof(IExceptionLogger), new ExLogger());
        app.UseWebApi(httpConfiguration);

        //Add Signalr Layer
        app.MapSignalR(new HubConfiguration
        {
            EnableJSONP = true,
            EnableDetailedErrors = true
        });
    }

    public class ExLogger : ExceptionLogger
    {
        public override void Log(ExceptionLoggerContext context)
        {
            base.Log(context);
            //do something
        }
    }
}