C# - 将内容复制到流时出错

Question

我有这个表格，其中有大约 10 个字段和最多 10 个图像。我将它们上传到服务器，大部分时间它都可以工作，但有时它会返回错误Error while copying content to a stream。

之后，当我重新启动应用程序并重试时，有时它可以工作，有时不能。

代码

// Image Path
var path_image_1 = await SecureStorage.GetAsync("image_1");

MultipartFormDataContent multiContent = new MultipartFormDataContent();
multiContent.Headers.ContentType.MediaType = "multipart/form-data";

// About 10 Fields like this
multiContent.Add(new StringContent(Email), "email");

// About 10 Images
var image_1 = File.ReadAllBytes(path_image_1);
multiContent.Add(new ByteArrayContent(image_1, 0, image_1.Count()), "images", path_image_1);


HttpClient httpClient = new HttpClient();
var response = await httpClient.PostAsync(url, multiContent);
string serverResponse = await response.Content.ReadAsStringAsync();

Answer 1

如果它有时有效，那么重试几次可能会有所帮助。如果您使用 polly nuget package，您可以将此代码包含在一个块中，该块将捕获异常和 retry 可配置的次数和可配置的等待时间。

var policy = Policy
.Handle<HttpRequestException>()
.Retry(3, onRetry: (exception, retryCount) =>
{
   Console.WriteLine($"retry Count is: {retryCount}");
});

policy.Execute(() => DoStuff());

然后你的实际逻辑将在一个单独的方法中：

public static void DoStuff()
{

// Image Path
   var path_image_1 = await SecureStorage.GetAsync("image_1");

   MultipartFormDataContent multiContent = new MultipartFormDataContent();
   multiContent.Headers.ContentType.MediaType = "multipart/form-data";

   // About 10 Fields like this
   multiContent.Add(new StringContent(Email), "email");

   // About 10 Images
   var image_1 = File.ReadAllBytes(path_image_1);
   multiContent.Add(new ByteArrayContent(image_1, 0, image_1.Count()), "images", path_image_1);


   HttpClient httpClient = new HttpClient();
   var response = await httpClient.PostAsync(url, multiContent);
   string serverResponse = await response.Content.ReadAsStringAsync();
}

Here 是一个展示它的基本示例。