OWIN has a concept of middleware. So does ASP.NET 5. Why? What is middleware? How does it help in typical web applications? In this talk we will dive into the code, write some middleware and show how middleware helps you handle cross-cutting concerns in an isolated and re-usable way. I'll compare and contrast the OWIN and ASP.NET 5 middleware concepts and talk about where each is appropriate.

2. Why Middleware?
Christian Horsdal
@chr_horsdal
www.horsdal-consult.dk

3. About me
Christian Horsdal
Independent Consultant
www.horsdal-consult.dk
c.horsdal@gmail.com
@chr_horsdal

4. Flexible
Componentized
Reusable
Testable

5. Web Applications Handle HTTP Requests
5

6. 6
Handler
Log request
Log response
Authenticate
Open DbContext
Close DbContext

7. Things You Might Do In the Pipeline
Open & dispose resources
Logging
Authentication
Authorization
Quick monitoring endpoints
Sanitize inputs
Content Negotiation
CORS
7

8. Things You Might Do In the Pipeline
Open & dispose resources
Logging
Authentication
Authorization
Quick monitoring endpoints
Sanitize inputs
Content Negotiation
CORS
8
Cross-cutting concerns
Re-use
Test separately
Update separately
Distribute separately

9. Do One Thing And Do It Well
9

10. Compose Pipeline
However You Want
10

11. 11
Handler
Log request
Log response
Authenticate
Open DbContext
Close DbContext
Minify HTML

12. OWIN

13. OWIN
• Open Web Interfaces for .NET
• Community driven standard
• Defines mechanics of pipeline
13

14. OWIN Terminology
Server
The web server
And/or an OWIN adapter
Middleware
Those pieces in the pipeline
Application
The handler
14

15. No shared assembly

16. OWIN Terminolgy
16
using AppFunc = Func<IDictionary<string, object>, Task>;

17. OWIN – Request Environment
Key Name
"owin.RequestBody"
"owin.RequestHeaders"
"owin.RequestMethod"
"owin.RequestPath"
"owin.RequestPathBase"
"owin.RequestProtocol"
"owin.RequestQueryString"
"owin.RequestScheme"

18. OWIN – Response Environment
Required Key Name
Yes "owin.ResponseBody"
Yes "owin.ResponseHeaders"
No "owin.ResponseStatusCode"
No "owin.ResponseReasonPhrase"
No "owin.ResponseProtocol"

19. OWIN Terminology
19
using MidFunc = Func<AppFunc, AppFunc>;
Handler
Log request
Log response
Authenticate
Open DbContext
Close DbContext

20. OWIN “Terminolgy”
20
using BuildFunc = Action<MidFunc>;

21. No shared assembly

22. 22

23. OWIN Middleware - As lambda
23
app.UseOwin(buildFunc => buildFunc(next => async ctx =>
{
var stopWatch = new Stopwatch();
stopWatch.Start();
await next(ctx);
WriteLine("Action execution time: " + stopWatch.ElapsedMilliseconds);
}));

24. OWIN Middleware – As lambda
24
app.UseOwin(buildFunc => buildFunc(next => ctx =>
{
if (ctx["owin.RequestPath"].Equals("/owin-middleware"))
{
var responseText = "Hello World";
var responseBytes = Encoding.UTF8.GetBytes(responseText);
var responseStream = (Stream)ctx["owin.ResponseBody"];
var responseHeaders = (IDictionary<string, string[]>)ctx["owin.ResponseHeaders"];
responseHeaders["Content-Length"] =
new string[] { responseBytes.Length.ToString(CultureInfo.InvariantCulture) };
responseHeaders["Content-Type"] = new string[] { "text/plain" };
return responseStream.WriteAsync(responseBytes, 0, responseBytes.Length);
}
return next(ctx);
}));

25. OWIN Middleware – As Class
25
app.UseOwin(buildFunc => buildFunc(next => new PerfLogMiddleware(next).Invoke));
public class PerfLogMiddleware
{
private readonly Func<IDictionary<string, object>, Task> next;
public PerfLogMiddleware(Func<IDictionary<string, object>, Task> next)
{
this.next = next;
}
public async Task Invoke(IDictionary<string, object> ctx)
{
var stopWatch = new Stopwatch();
stopWatch.Start();
await next(ctx);
WriteLine("Action execution time: " + stopWatch.ElapsedMilliseconds);
}
}

26. ASP.NET 5 Middleware
But, wait. Wasn’t OWIN the middleware thing?
There is a bridge
26

27. ASP.NET 5 Middleware
27
app.Use(next => async ctx =>
{
if (ctx.Request.Path == "/aspnet-middleware/" )
{
ctx.Response.ContentType = "text/html";
ctx.Response.StatusCode = 200;
await ctx.Response.WriteAsync("Hello Middleware as lambda");
return;
}
await next(ctx);
});

28. ASP.NET 5 Middleware
28
app.Use(next => new PerfLogAspnetMiddleware(next).Invoke);
private class PerfLogAspnetMiddleware
{
private RequestDelegate next;
public PerfLogAspnetMiddleware(RequestDelegate next)
{
this.next = next;
}
public async Task Invoke(HttpContext ctx)
{
var stopWatch = new Stopwatch();
stopWatch.Start();
await next(ctx);
WriteLine("Action execution time: " + stopWatch.ElapsedMilliseconds);
}
}

29. 29
OWIN and Web Frameworks

30. Compatible Frameworks
• ASP.NET MVC 5 & 6
• WebApi
• Nancy
• Simple.Web
30

31. ASP.NET 5
31
public class Startup
{
public void Configure(IApplicationBuilder app)
{
app.UseOwin();
}
}

32. ASP.NET < 5 + Katana
32
public class Startup
{
public void Configuration(IAppBuilder builder)
{
builder.Use(new MidFunc(next => (AppFunc)Invoke));
}
public Task Invoke(IDictionary<string, object> environment)
{
…
}
}

33. Katana
33
public class Startup
{
public void Configuration(IAppBuilder app)
{
app.Run(Invoke);
}
public Task Invoke(IOwinContext context)
{
context.Response.ContentType = "text/plain";
return context.Response.WriteAsync("Hello World");
}
}

34. WebApi + Katana
34
Katana startup.cs code
public class Startup
{
public void Configuration(IAppBuilder builder)
{
HttpConfiguration config = new HttpConfiguration();
config.Routes
.MapHttpRoute("Default", "{controller}/{id}",
new { controller = "Home", id = RouteParameter.O
config.Formatters.XmlFormatter.UseXmlSerializer = true;
config.Formatters.Remove(config.Formatters.JsonFormatter);
builder.UseWebApi(config);
}
}

35. OWIN Testing
Integration test the complete pipeline
Integration test parts of the pipeline
While in process
35

36. 36
Handler
Log request
Log response
Authenticate
Open DbContext
Close DbContext
Minify HTML

37. Christian Horsdal
@chr_horsdal
www.horsdal-consult.dk

38. webnextconf.eu