netcore GetAsync 下載文件流

[HttpGet]
        public async Task<IActionResult> Get4()
        {
            var client = _httpClientFactory.CreateClient();
            var resp = await client.GetAsync("http://localhost:99/api/httpfile/GetFile");
            var con_dis = resp.Content.Headers.Where(o => o.Key == "Content-Disposition").Select(m => m.Value).FirstOrDefault().FirstOrDefault();
            Regex regex = new Regex("filename=(.+);");
            var filename = regex.Match(con_dis).Groups[1].Value;
            var ext = filename.Split('.').Reverse().First();
            new FileExtensionContentTypeProvider().Mappings.TryGetValue("." + ext, out var contenttype);
            var buffer = await resp.Content.ReadAsByteArrayAsync();
            return File(buffer, contenttype, filename);
        }

可以直接下載文件