Understanding the ASP.NET Core Request Pipeline

Every HTTP request in an ASP.NET Core app flows through something called the middleware pipeline and if you understand it, you can unlock serious control over how your app behaves.

In this post, I’ll break down what the request pipeline is, how middleware works, and how you can customize it like a pro.

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🧱 What Is Middleware?

Middleware is like a conveyor belt; each step (or middleware) does something to the request, then passes it on.

It can:

• ✅ Authenticate a user
• ✅ Log a request
• ✅ Handle errors
• ✅ Modify the request or response

Each middleware decides whether to:

• Continue to the next step (await next();)
• Short-circuit the pipeline and end the response

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🔁 Default Pipeline Example

In a typical Program.cs, you'll see:

var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();

app.UseHttpsRedirection();
app.UseAuthorization();
app.MapControllers();

app.Run();

Each app.Use... line is a middleware. They run in the order you add them so order matters!

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✍️ Writing Your Own Middleware

Custom middleware is easy to build:

public class RequestLoggerMiddleware
{
    private readonly RequestDelegate _next;

    public RequestLoggerMiddleware(RequestDelegate next)
    {
        _next = next;
    }

    public async Task InvokeAsync(HttpContext context)
    {
        Console.WriteLine($"[{DateTime.Now}] Request: {context.Request.Method} {context.Request.Path}");
        await _next(context);
    }
}

Register it like this:

app.UseMiddleware<RequestLoggerMiddleware>();

Boom — you’ve just inserted a custom step into your pipeline.

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⚠️ Common Pitfalls

• 🔁 Order of middleware matters (e.g., UseRouting must come before UseEndpoints)
• 🔒 Put UseAuthentication() before UseAuthorization()
• 🧪 Test your custom middleware in isolation

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💡 Real-World Use Cases

• Logging with Serilog
• Custom exception handling
• Multi-tenancy or per-request headers
• Feature flags

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✅ Up Next

Now that you understand the pipeline, we’ll explore routing how your app maps incoming requests to specific logic.

➡️ Routing in ASP.NET Core Made Easy →

Follow the series to keep getting better, one layer at a time 💪