问RestSharp“错误获取响应流(ReadAsync)：ReceiveFailure值不能为空。参数名称: src”

EN

public class MyRestClient : RestClient
{
    public MyRestClient(string baseUrl) : base(baseUrl)
    { }

    public override IRestResponse Execute(IRestRequest request)
    {
        request.ResponseWriter = s => { };
        request.AdvancedResponseWriter = (input, response) => response.RawBytes = ReadAsBytes(input);

        return base.Execute(request);
    }

    private static byte[] ReadAsBytes(Stream input)
    {
        var buffer = new byte[16 * 1024];

        using (var ms = new MemoryStream())
        {
            int read;
            try
            {
                while ((read = input.Read(buffer, 0, buffer.Length)) > 0)
                { ms.Write(buffer, 0, read); }

                return ms.ToArray();
            }
            catch (WebException ex)
            { return Encoding.UTF8.GetBytes(ex.Message); }
        };
    }
}

//payload am sending to the api 
   RequestPayload res = new RequestPayload();
   res.appid = appid;
   res.data = data;
   res.method = "Login";

   //convert to json object
   var MySerializedObject =  JsonConvert.SerializeObject(res);

   string APIUrl = ""http://142.168.20.15:8021/RouteTask";

   //create basic .net http client
   HttpClient client = new HttpClient();
   client.BaseAddress = new Uri(APIUrl);

   // this was required in the header of my request, 
   // you may not need this, or you may need to adjust parameter
   //("RequestSource","Web") or you own custom headers
   client.DefaultRequestHeaders.Add("RequestSource", "Web");
    // this class is custom, you can leave it out
   connectionService = new ConnectionService();
  //check for internet connection on users device before making the call
  if (connectionService.IsConnected)
    {
       //make the call to the api
        HttpResponseMessage response = await 
        client.PostAsJsonAsync(ApiConstants.APIDefault, res);
        if (response.IsSuccessStatusCode)
            {
                string o = response.Content.ReadAsStringAsync().Result;
                dynamic payload = JsonConvert.DeserializeObject(o);
                string msg = payload["valMessage"];
                resp.a = true;
                resp.msg = payload["responseDescription"];
            }
        else
            {
                string o = response.Content.ReadAsStringAsync().Result;
                dynamic payload = JsonConvert.DeserializeObject(o);
                resp.a = false;
                resp.msg = payload["response"];
            }
    }