ASP.NET Core Middleware: A Complete Guide

ASP.NET Core is a high-performance, cross-platform web framework developed by Microsoft. One of its most powerful and flexible features is middleware, which plays a central role in handling HTTP requests and responses in the application pipeline. In this article, we'll explore:

1. What is middleware is
2. How the request pipeline works
3. How to create custom middleware
4. Real-world examples
5. Best practices

ASP.NET Core Middleware: A Complete Guide

Getting Started

Middleware is one of the most powerful features in ASP.NET Core. It enables a clean, pluggable, and modular way of handling HTTP requests. Whether you're serving static files, authenticating users, logging, or modifying responses — middleware is where it happens.

In ASP.NET Core, middleware is software that's assembled into an application pipeline to handle requests and responses. You can say middleware in .net core is a sequence of plumbing stpes where each step can modify the request, produce a response, or both. Some middleware might short-circuit the pipeline without calling the next step. For example, a middleware can return an error or service a static file.

What is Middleware In .Net Core?

Middleware in .Net Core is a key concept in request processing pipeline. It is a software that is executed in sequence to handle HTTP requests and responses as part of a pipeline. Each middleware component in the pipeline has a specific purpose and can

• Receives an HTTP request.
• Optionally calls the next middleware in the pipeline
• Or modify the request/response before or after the next component runs.

Common Purposes of Middleware In ASP.Net.Core

• Logging
• Exception handling
• Request/response modification
• CORS handling
• Security (authentication, authorization)
• Performance metrics

Common Built-in ASP.NET Core Middleware Components

ASP.NET Core provides several built-in middleware components, some of the middlewares are listed below:

1. UseStaticFiles(): Serves static files like CSS, JS, images
2. UseRouting(): Enables routing for endpoints
3. UseAuthentication(): Authentication middleware in net.core validates user identity
4. UseAuthorization():Authorization middleware in net.core Checks access permissions
5. UseCors(): Enables Cross-Origin Resource Sharing
6. UseExceptionHandler(): Handles unhandled exceptions globally
7. UseHttpsRedirection(): Redirects HTTP requests to HTTPS

Custom Middleware In .Net.Core

You can create your own middleware for tasks like logging, request modification, or error handling. Custom middleware in .Net Core can be written as inline delegates, but for cleaner and reusable code, it is good practice to create a dedicated class.

Create a Custome Middleware

The below code example is a custom middleware is created for loggin in ASP.NET Core application.

public class LoggingMiddleware  
 {  
   private readonly RequestDelegate _next;  
   public LoggingMiddleware(RequestDelegate next)  
   {  
     _next = next;  
   }  
   public async Task InvokeAsync(HttpContext context)  
   {  
     Console.WriteLine($"Incoming request: {context.Request.Method} {context.Request.Path}");  
     await _next(context); // Call the next middleware  
     Console.WriteLine($"Response status: {context.Response.StatusCode}");  
   }  
 }  

Registering Custome Middleware

app.UseMiddleware<LoggingMiddleware>(); 

Summary

Middleware in ASP.NET Core provides a powerful way to compose the behavior of your application. By understanding how middleware works and how to write your own, you gain fine-grained control over the HTTP pipeline, making your application more modular, testable, and maintainable. I hope this was helpful to you

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