OWIN Startup Class - dependency-injection

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
}
}
}