How do you write a custom middleware?

Short answer: Create a class with: A constructor accepting RequestDelegate An Invoke or InvokeAsync method public class MyCustomMiddleware { private readonly RequestDelegate _next; public MyCustomMiddleware(RequestDelegate next) => _next = next; public async Task InvokeAsync(HttpContext context) { // Pre-processing logic await _next(context); // Post-processing logic } } Register it: app.UseMiddleware<MyCustomMiddleware>();

Example code

Create a class with: A constructor accepting RequestDelegate An Invoke or InvokeAsync method public class MyCustomMiddleware
{
private readonly RequestDelegate _next;
public MyCustomMiddleware(RequestDelegate next) => _next = next; public async Task InvokeAsync(HttpContext context)
{ // Pre-processing logic await _next(context); // Post-processing logic }
} Register it: app.UseMiddleware<MyCustomMiddleware>();

Real-world example (ShopNest)

ShopNest pipeline order matters: exception handling → HTTPS → auth → authorization → endpoints. Auth must run before protected APIs.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.