"c#" "core" SOAP MTOM

 public static MtomObject MtomCall(this string s, string endPoint, string soapMethod)
        {
            var client = new HttpClient();
            List<MtomAttachment> enumerable;

            byte[] firstOrDefault;
            using (var requestMessage =
                new HttpRequestMessage(HttpMethod.Post, endPoint))
            {
                requestMessage.Content = new StringContent(s, Encoding.UTF8);
                requestMessage.Headers.Add("ContentType", "application/xop+xml;charset=utf-8;type=\"text/xml\"");
                requestMessage.Headers.Add("MIME-Version", "1.0");
                requestMessage.Headers.Add("SOAPAction", soapMethod);
                var multipartMemoryStreamProvider = client.SendAsync(requestMessage).Await().Content.ReadAsMultipartAsync().Await();
                firstOrDefault = multipartMemoryStreamProvider.Contents.FirstOrDefault()?.ReadAsByteArrayAsync().Await();
                enumerable = multipartMemoryStreamProvider.Contents.Skip(1).Select(
					//solution dependent 
                    x=> new MtomAttachment { Bytes=x.ReadAsByteArrayAsync().Await(),ContentId = x.Headers.FirstOrDefault(y => y.Key=="Content-ID").Value.FirstOrDefault()?.Replace("<","").Replace(">", "") }).ToList();
            }
            return new MtomObject {
                Body = System.Text.Encoding.UTF8.GetString(firstOrDefault),
                Attachments = enumerable };
        }

 public class MtomObject
    {
        
        internal string Body { get; set; }
        internal  List<MtomAttachment> Attachments{get;set; }
        
    }
    public partial class MtomAttachment
    {
        internal byte[] Bytes { get; set; }
        internal  string ContentId {get;set; }
    }

 public static class Awaitable
    {
        public static T Await<T>(this Task<T> task, int? timeout = null)
        {
            if (timeout != null)
            {
                task.Wait(new TimeSpan(0, 0, 0, 0, (int)timeout));
            }
            else
            {
                task.Wait();
            }
            return task.Result;
        }
    }