we will understand how to set up middleware. Middleware in ASP.NET Core controls how our application responds to HTTP requests. It can also control how our application looks when there is an error, and it is a key piece in how we authenticate and authorize a user to perform specific actions.

 

• Middleware are software components that are assembled into an application pipeline to handle requests and responses.

• Each component chooses whether to pass the request on to the next component in the pipeline, and can perform certain actions before and after the next component is invoked in the pipeline.

• Request delegates are used to build the request pipeline. The request delegates handle each HTTP request.

• Each piece of middleware in ASP.NET Core is an object, and each piece has a very specific, focused, and limited role.

• Ultimately, we need many pieces of middleware for an application to behave appropriately.

• Let us now assume that we want to log information about every request into our application.

• In that case, the first piece of middleware that we might install into the application is a logging component.

• This logger can see everything about the incoming request, but chances are a logger is simply going to record some information and then pass along this request to the next piece of middleware.

• Middleware is a series of components present in this processing pipeline.

• The next piece of middleware that we've installed into the application is an authorizer.

• An authorizer might be looking for specific cookie or access tokens in the HTTP headers.

• If the authorizer finds a token, it allows the request to proceed. If not, perhaps the authorizer itself will respond to the request with an HTTP error code or redirect code to send the user to a login page.

• But, otherwise, the authorizer will pass the request to the next piece of middleware which is a router.

• A router looks at the URL and determines your next step of action.

• The router looks over the application for something to respond to and if the router doesn't find anything to respond to, the router itself might return a 404 Not Found error.

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