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.
What are the ASP.NET Core Middleware Components?
The ASP.NET Core Middleware Components are the software components (technically components are nothing but the C# Classes) that are assembled into the application pipeline to handle the HTTP Requests and Responses. Each middleware component in ASP.NET Core Application performs the following tasks.
1.Chooses whether to pass the HTTP Request to the next component in the pipeline. This can be achieved by calling the next() method within the middleware.
2.Can perform work before and after the next component in the pipeline.
In ASP.NET Core there are so many built-in Middleware components that are already made available that you can use directly. If you want then you can also create your own Middleware components in asp.net core applications. The most important point that you need to keep in mind is, in ASP.NET Core a given Middleware component should only have a specific purpose i.e. single responsibility.
The Middleware components are the components that we generally use to set up the request processing pipeline in the ASP.NET Core application.
Where we use Middleware Components in the ASP.NET Core application?
Some of the examples of using Middleware components in the ASP.NET Core application are as follows :-
We may have a Middleware component for authenticating the user
Another Middleware component may be used to log the request and response
Similarly, we may have a Middleware component that is used to handle the errors
We may have a Middleware component that is used to handle the static files such as images, Javascript or CSS files, etc.
Another Middleware component may be used to Authorize the users while accessing a specific resource
How to Configure Middleware Components in ASP.NET Core application?
In the ASP.NET Core application, we need to configure the Middleware components within the Configure() method of the Startup class which is present inside the Startup.cs file.
So, whenever you want to configure any middleware components in any type of .net core applications, then you need to configure it within the Configure() method of the Startup class by calling the Use* methods on the IApplicationBuilder object.
Understanding Middleware Components in ASP.NET Core:
In the ASP.NET Core application, the Middleware component can have access to both the incoming HTTP Request and outgoing HTTP Response. So, a Middleware component in ASP.NET Core can
Handle the incoming HTTP request by generating an HTTP response.
Process the incoming HTTP request, modify it, and then pass it to the next middleware component
Process the outgoing HTTP response, modify it, and then pass it on to either the next middleware component or to the ASP.NET Core web server.
A middleware component in ASP.NET Core may also handle the HTTP Request by generating an HTTP Response. The ASP.NET Core Middleware component may also decide not to call the next middleware component in the request pipeline.
For example, we have a static file middleware component. And if the incoming HTTP request comes for some static files such as images, CSS files, JavaScript, etc. then this Static Files Middleware component can handle the request and then short-circuit the request pipeline by not calling to the next component in the pipeline i.e. the MVC Middleware component.
As we already discussed the ASP.NET Core middleware components can have access to both the HTTP request and response in the pipeline. So, a middleware component can also process the outgoing response. For example, the logging middleware component in our case may log the time when the response is sent back to the client.
It is very important to understand the execution order of Middleware components. The ASP.NET Core middleware components are executed in the same order as they are added to the pipeline.
As per your application’s business requirements, you may add any number of Middleware components. For example, if you are developing a static web application with some static HTML pages and images, then you may require only “StaticFiles” middleware components in the request processing pipeline.
But, if you are developing a secure dynamic data-driven web application then you may require several middleware components such as Logging Middleware, Authentication middleware, Authorization middleware, MVC middleware, etc.
In ASP.NET Core, you can use the “Use” and “Run” extension methods to register the Inline Middleware component into the Request processing pipeline. The “Run” extension method allows us to add the terminating middleware. On the other hand, the “Use” extension method allows us to add the middleware components which may call the next middleware component in the request processing pipeline.
What is the difference between MapGet and Map method?
The MapGet method is going to handle the GET HTTP Requests whereas the Map method is going to handle all types of HTTP requests such as GET, POST, PUT, & DELETE, etc.
