互联网断开连接时，HttpClient PostAsync不响应

Question

我有一个xamarin表单应用，应用程序执行PostAsync调用以将图像上传为多部分内容。

问题是在iOS设备中，当我在PostAsync调用期间关闭wifi /移动数据时，HttpClient不会进入catch块以指示异常。它只在默认超时100秒后才会这样做。

但Android中不会出现此问题，并且成功进入catch块，表示System.IO.IOException

这是执行PostAsync调用的代码，我是否遗漏了什么或做错了什么。谢谢。

 try{
 MultipartFormDataContent multipartContent = new MultipartFormDataContent();
 var uri = new Uri(string.Format(strUrl + "UserData/SavePointRequestData/", string.Empty));

 StringContent strPointsRequestIDContent = new StringContent(oPointRequest.PointsRequestID.ToString());
 multipartContent.Add(strPointsRequestIDContent, "strPointsRequestID");
 if (bImageData != null) {
  var PointRequestfileContent = new ByteArrayContent(bImageData);
  PointRequestfileContent.Headers.ContentType = MediaTypeHeaderValue.Parse("application/octet-stream");
  PointRequestfileContent.Headers.ContentDisposition = new ContentDispositionHeaderValue("form-data") {
   FileName = strActualImageName + ".jpg"
  };
  multipartContent.Add(PointRequestfileContent, "strUploadImage");
 }

 HttpClient client = new HttpClient();
 HttpResponseMessage response = await client.PostAsync(uri, multipartContent);
 if (response.IsSuccessStatusCode) {
  using(var stream = await response.Content.ReadAsStreamAsync()) {
   using(var streamreader = new StreamReader(stream)) {
    var str = await streamreader.ReadToEndAsync();
    var obj = await JsonConvert.DeserializeObjectAsync < string > (str);
    return obj;
   }
  }
 } else {
  return "Error1" + "," + oPointRequest.EventActivityName.ToString();
 }
 } 
catch (Exception ex) {
  System.Diagnostics.Debug.WriteLine(e.Message);


  return "Error2" + "," + oPointRequest.EventActivityName.ToString();
 }