Question

How can you create and use custom middleware components in a .NET Core application? What is a practical scenario for implementing custom middleware?

Answer 1

To create custom middleware in .NET Core, follow these steps:

1. Create a class with Invoke or InvokeAsync method, taking HttpContext as a parameter.
2. Use extension methods to add the middleware to the pipeline.

Example:

public class CustomMiddleware

{

private readonly RequestDelegate _next;

public CustomMiddleware(RequestDelegate next)

{

_next = next;

}

public async Task InvokeAsync(HttpContext context)

{

// Middleware logic here

await _next(context);

}

}

public static class CustomMiddlewareExtensions

{

public static IApplicationBuilder UseCustomMiddleware(this IApplicationBuilder builder)

{

return builder.UseMiddleware<CustomMiddleware>();

}

}

In Startup.cs, use the extension method within Configure method:

app.UseCustomMiddleware();

A practical scenario for implementing custom middleware is logging and exception handling. Custom middleware can intercept requests and responses, allowing centralized logging of incoming requests, outgoing responses, and exceptions that occur during processing.