Modify response using middleware in ASP.NET Core 3 - asp.net-core

Question

My goal is to write a middleware that will take care of logging requests to my API and API's responses to those requests in a DB.
I already made a middleware that handles exceptions in a similar fashion, but I got stumped over this.
When you read MSDN about Middleware you can see this nice picture:
This makes you think that Middleware 2 receives the requests, does certain manipulations with it and passes it onto Middleware 3, then once all processing is done by middleware 3 it passes controls back to Middleware 2 for additional processing.
The only thing I do not understand is how to log the response if Middleware 2 Invoke() method is only called once during the request and not called during the response?
Startup.cs:
app.UseMiddleware<RequestLoggingMiddleware>();
Middleware:
public class RequestLoggingMiddleware
{
private readonly RequestDelegate nextMiddleware;
public RequestLoggingMiddleware(RequestDelegate nextMiddleware)
{
this.nextMiddleware = nextMiddleware;
this.options = options;
}
public async Task Invoke(HttpContext context)
{
System.Diagnostics.Debug.WriteLine("Middleware runs");
await nextMiddleware(context);
}
}
}
In the example above I only see "Middleware runs" once in a console, during the initial request but before the response is made. How do I get it to run during the response cycle?

Answer 1

To get the response, all you need to do is apply your same logic after the await nextMiddleware(context); line.
For example, to log the status code:
public class RequestLoggingMiddleware
{
private readonly RequestDelegate nextMiddleware;
public RequestLoggingMiddleware(RequestDelegate nextMiddleware)
{
this.nextMiddleware = nextMiddleware;
}
public async Task Invoke(HttpContext context)
{
System.Diagnostics.Debug.WriteLine("Middleware runs");
await nextMiddleware(context);
System.Diagnostics.Debug.WriteLine($"Response Code: {context.Response.StatusCode}");
}
}