Samples of middleware

NoOwinDllReference.cs

    using AppAction = Func<
        IDictionary<string, object>,
        IDictionary<string, string[]>,
        Stream,
        Task<Tuple<
            IDictionary<string, object>,
            int,
            IDictionary<string, string[]>,
            Func<Stream, Task>>>>;

public static class DefaultContentType
{
  // one way you can write parameterized middleware - returns the chaining method

  public static Func<AppAction, AppAction> Middleware(string contentType)
  {
    // "next app" passed once at startup-time
    // additional parameters passed per-call

    return app => async (env, headers, input) =>
    {
        // examine/alter call parameters here

        // call to the next app in pipeline
        var result = await app(env, headers, input);

        // examine/alter result parameters here
        if (!result.Item3.ContainsKey("Content-Type"))
        {
            result.Item3["Content-Type"] = new[] { contentType };
        }

        return result;
    };
  }

  // can be overloaded

  public static Func<AppAction,AppAction> Middleware()
  {
    return Middleware("text/html");
  }  
}

Sample.cs

// example middleware with owin.dll reference

using Owin;

public static class BlueGreen
{

  // static method used to chain
  
  public static AppDelegate Middleware(AppDelegate app)
  {
    return async call =>
    {
      // examine and/or adjust call

      var result = await app(call);

      // examine and/or adjust result

      return result;
    }
  }
 
  // syntax sugar to give builder.UseBlueGreen() and intellisense

  public static AppDelegate UseBlueGreen(this IAppBuilder builder)
  {
    return builder.Use<AppDelegate>(Middleware);
  }
}

Usage.cs

using Owin;

public class Startup
{
  public void Configuration(IAppBuilder builder)
  {
    // use BlueGreen middleware via extension method
    builder.UseBlueGreen();

    // use DefaultContentType middleware via chaining function
    builder.Use(DefaultContentType.Middleware("text/plain"));

  }
}