vNext Owin Middleware

Question

I have a simple middleware:

public class MiddlewareInterceptor
{
    RequestDelegate _next;
    public MiddlewareInterceptor(RequestDelegate next)
    {
        _next = next;
    }

    public Task Invoke(HttpContext ctx)
    {
        ctx.Response.WriteAsync("<h2>From SomeMiddleWare</h2>");
        return _next(ctx);
    }
}

And in my Startup.cs Configure method, I hook it like so:

app.UseMiddleware<MiddlewareInterceptor>();

The above builds and the app seems to run fine, but my breakpoint in the interceptor Invoke method never hits. And likewise, there is never any output. I tried that with Debug.WriteLine also.

Now, I also tried this method:

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

    public override async Task Invoke(IOwinContext context)
    {
        Debug.WriteLine(context.Request.Uri.ToString());
        await Next.Invoke(context);
    }
}

And in my Startup.cs Configure method, I hook it like so:

app.Use(next => new MiddlewareInterceptor(next).Invoke);

Unfortunately, the base OwinMiddleware constructor is looking for the next OwinMiddleware as a parameter, unlike ye olde RequestDelegate. So my app.Use instantiation of my MiddlewareInterceptor fails because next is of type RequestDelegate.

Lastly, I have tried an inline function directly in the Configure method which also never hits the breakpoint:

app.Use(async (ctx, next) =>
{
    System.Diagnostics.Debug.WriteLine("Hello");
    await next();
});

So as it stands, it seems like I cant make a basic middleware interceptor using OWIN. What am I missing?

Answer 1

What is the order of the aforementioned middleware in the pipeline? Make sure this executes before anything that will terminate the request part of the pipeline; eg. UseMvc();