How C# ASP.NET Core Middleware is different from HttpModule?

In ASP.NET Core, middleware replaces the traditional HttpModules used in classic ASP.NET. While both serve as components that handle HTTP requests and responses, they differ significantly in configuration, execution control, and architecture.

Key Differences Overview

HttpModules are event-driven components tied to the ASP.NET application lifecycle, while middleware components form a pipeline where each component can handle requests before passing them to the next component in the chain.

Detailed Comparison

Built-in ASP.NET Core Middleware

• Authentication − Provides authentication support for validating user credentials.

• CORS − Configures Cross-Origin Resource Sharing policies for web APIs.

• Routing − Defines and constrains request routes to appropriate controllers and actions.

• Session − Provides support for managing user sessions and state.

• Diagnostics − Includes support for error pages and runtime information display.

Creating Custom Middleware

Basic Middleware Implementation

using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;
using System.Threading.Tasks;

public class MyMiddleware {
    private readonly RequestDelegate _next;
    private readonly ILogger _logger;
    
    public MyMiddleware(RequestDelegate next, ILoggerFactory logFactory) {
        _next = next;
        _logger = logFactory.CreateLogger("MyMiddleware");
    }
    
    public async Task Invoke(HttpContext httpContext) {
        _logger.LogInformation("MyMiddleware executing..");
        await _next(httpContext); // calling next middleware
    }
}

Extension Method for Middleware Registration

using Microsoft.AspNetCore.Builder;

public static class MyMiddlewareExtensions {
    public static IApplicationBuilder UseMyMiddleware(this IApplicationBuilder builder) {
        return builder.UseMiddleware<MyMiddleware>();
    }
}

Registering Middleware in Startup.cs

using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.Http;

public class Startup {
    public void Configure(IApplicationBuilder app, IWebHostEnvironment env) {
        app.UseMiddleware<MyMiddleware>();
        
        app.Run(async (context) => {
            await context.Response.WriteAsync("Hello World!");
        });
    }
}

Conclusion

ASP.NET Core middleware provides better control, flexibility, and performance compared to HttpModules. The pipeline-based architecture allows developers to configure components in any order and provides a more modular, testable approach to handling HTTP requests and responses in modern web applications.