json - httpclient 502 错误 xamarin 应用程序通过 json 传输照片

Question

当我们尝试在 Json 中发送照片时，我们收到 502 错误。使用 .NET 和 Xamarin.Form 开发的应用程序

var jsonObjGuid = JsonConvert.SerializeObject(ObjGuid);
var jsonObjFiles = JsonConvert.SerializeObject(ObjFiles, Formatting.Indented);
var url = $"{ Session.EndpointURL}{MethodNames.UploadDossierFiles.Value}";

try
{
    using (HttpClient httpClient = new HttpClient())
    {
        httpClient.DefaultRequestHeaders.TransferEncodingChunked = true;
        httpClient.Timeout = TimeSpan.FromMilliseconds(600000);

        using (HttpRequestMessage request = new HttpRequestMessage(HttpMethod.Post, url))
        {
            //request.Headers.Add(HeaderKeys.UserAgent.Value, Resources.DefaultUserAgent);
            request.Headers.Add(HeaderKeys.UserAgent.Value, "MobileApp");
            request.Headers.Add(HeaderKeys.Token.Value, token);

            HttpContent ObjGuidContent = new StringContent(jsonObjGuid);
            HttpContent ObjFilesContent = new StringContent(jsonObjFiles);

            MultipartFormDataContent content = new MultipartFormDataContent
                {
                    {ObjGuidContent, "ObjGuid"},
                    {ObjFilesContent, "ObjFiles"}
                };

            request.Content = content;
            var response = await Policy.HandleResult<HttpResponseMessage>(message => !message.IsSuccessStatusCode)
                .WaitAndRetryAsync(3, i => TimeSpan.FromSeconds(2), (result, timeSpan, retryCount, context) => { })
                .ExecuteAsync(() => httpClient.SendAsync(request));
        }
    }
}

有时它有效，但我经常收到此错误。任何帮助，建议？我需要检查什么？