We will explore all aspect of middleware building in this section.

• Middleware 0

  ASP.NET Core is built on top of pipelines of functions called middleware. This sample shows the basic outline on how they work.

  We are using IApplicationBuilder Use, an extension method for adding middleware and IApplicationBuilder Run.

• Middleware 1

  This example shows how to pass information from one middleware to another using HttpContext.Items.

• Middleware 2

  As a general rule, only one of your Middleware should write to Response in an execution path. This sample shows how to work around this by buffering the Response.

  e.g.

  If path / involves the execution of Middleware 1, Middleware 2 and Middleware 3, only one of these should write to Response.

• Middleware 3

  This is the simplest middleware class you can create.

• Middleware 4

  Use app.Map (MapMiddleware) to configure your middleware pipeline to respond only on specific url path.

• Middleware 5

  Nested app.Map (show Request.Path and Request.PathBase).

• Middleware 6

  Use app.MapWhen(MapWhenMiddleware) and Nested app.Map (show Request.Path and Request.PathBase).

• Middleware 7

  Use MapMiddleware and MapWhenMiddleware directly without using extensions (show Request.Path and Request.PathBase).

• Middleware 8

  Demonstrate the various ways you can inject dependency to your middleware class manually.

• Middleware 9

  Demonstrate how to ASP.NET Core built in DI (Dependency Injection) mechanism to provide dependency for your middleware.

• Middleware 10

  Demonstrate that a middleware is a singleton.

• Middleware 11

  This sample is similar to Middleware 10 except that this one implement IMiddleware to create Factory-based middleware activation. This means that you can create a middleware that is not a singleton (either Transient or Scoped).

• Middleware 12

  Contrast the usage of MapWhen (which branch execution) and UseWhen (which doesn't branch execution) in configuring your Middleware.

• Middleware 13

  Demonstrate how to implement basic error handling mechanism and how to return error object (same for all api exceptions).

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