How to GZip Compress an HttpResponse manually in an Action Filter in .NET 5?

Question

First off, I know I could just use the built-in middleware (ie app.UseResponseCompression();), but I'm having to do this to support a legacy application.

This was code used by API in old .NET framework using System.Web.Http.Filters:

public override void OnActionExecuted(HttpActionExecutedContext actContext)
    {
        HttpContext.Current.Response.Filter = new System.IO.Compression.GZipStream(HttpContext.Current.Response.Filter, System.IO.Compression.CompressionMode.Compress);
        actContext.Response.Content.Headers.Add("Content-encoding", "gzip");
        base.OnActionExecuted(actContext);
    }

Anyone know how I could replicate that using Microsoft.AspNetCore.Mvc.Filters? I have this so far, can't figure out how to do the actual compression part.

public override async void OnActionExecuted(ActionExecutedContext context)
    {
        var response = context.HttpContext.Response;
        //Below line doesn't work, but anywhere close?
        //response.Body = new GZipOutputStream(response.Body);
        response.Headers.Add("Content-Encoding", "gzip");
        base.OnActionExecuted(context);
    }

Answer 1

It seems that it cannot be done. The approach used in the middleware (like this) in which you pass a custom stream before the "next" doesn't work. The body il always put in the memory location of the "Response.Body".