我相当确定我在我的应用程序中造成了死锁,但我不确定如何解决该问题。我有一些事件部件并且是 async
和 await
的新手,所以请多多包涵。
我有一个客户端上传文件如下:
public static async Task<string> UploadToService(HttpPostedFile file, string authCode, int id)
{
var memoryStream = new MemoryStream();
file.InputStream.CopyTo(memoryStream);
var requestContent = new MultipartFormDataContent();
var fileContent = new ByteArrayContent(memoryStream.ToArray());
fileContent.Headers.ContentType = MediaTypeHeaderValue.Parse(file.ContentType);
requestContent.Add(fileContent, "file", file.FileName);
using (var httpClient = new HttpClient())
{
httpClient.BaseAddress = new Uri(BaseUrl);
httpClient.DefaultRequestHeaders.Accept.Clear();
var message =
await
httpClient.PostAsync(
string.Format("Upload?authCode={0}&id={1}", authCode, id),
requestContent);
return await message.Content.ReadAsStringAsync();
}
}
接收文件的piece:
[HttpPost]
public Task<HttpResponseMessage> Upload(string authCode, int id)
{
var request = Request;
var provider = new CustomMultipartFormDataStreamProvider(root);
var task =
request.Content.ReadAsMultipartAsync(provider)
.ContinueWith(o =>
{
// ...
// Save file
// ...
return new HttpResponseMessage()
{
Content = new StringContent("File uploaded successfully"),
StatusCode = HttpStatusCode.OK
};
});
return task;
}
一切从以下开始:
protected void Page_Load(object sender, EventArgs e)
{
if (IsPostBack)
{
var file = HttpContext.Current.Request.Files[0];
var response = UploadToService(file, hiddenAuthCode.Value, int.Parse(hiddenId.Value));
}
}
除了 PostAsync
从未识别出 task
已返回外,一切似乎都正常。我可以看到 await ... PostAsync ...
任务的状态是 WaitingForActivation 但我不完全确定那是什么意思(记住,我对这东西一窍不通)。我的文件已保存到正确的位置,但应用程序始终无法识别来 self 的服务的响应。
如果有人能指出正确的方向,我将不胜感激。
最佳答案
我认为问题在于您只需调用 UploadToService
内部以即发即弃的方式Page_Load
.请求处理在此任务完成之前简单地结束。
你应该使用 <%@ Page Async="true" ...>
在此 WebForms 页面中并包含 <add key="aspnet:UseTaskFriendlySynchronizationContext" value="true" />
在你的web.config
那里。
然后使用RegisterAsyncTask
,代码将如下所示:
protected void Page_Load(object sender, EventArgs e)
{
if (IsPostBack)
{
var file = HttpContext.Current.Request.Files[0];
RegisterAsyncTask(new PageAsyncTask(() => UploadToService(file,
hiddenAuthCode.Value, int.Parse(hiddenId.Value))));
}
}
附带说明一下,您可以改进这部分:
file.InputStream.CopyTo(memoryStream);
像这样:
await file.InputStream.CopyToAsync(memoryStream);
并替换ContinueWith
与 async/await
:
[HttpPost]
public async Task<HttpResponseMessage> Upload(string authCode, int id)
{
var request = Request;
var provider = new CustomMultipartFormDataStreamProvider(root);
await request.Content.ReadAsMultipartAsync(provider);
return new HttpResponseMessage()
{
Content = new StringContent("File uploaded successfully"),
StatusCode = HttpStatusCode.OK
};
}
关于c# - 异步死锁?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/24879340/