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从任务中自动删除等待时,SendAsync失败

httpclient task asynchronous .net c#

-1

Itamar Kerbel · 技术社区 · 5 年前

 using (StringContent stringContent = new StringContent(payload, Encoding.UTF8, "application/json"))
 {
     HttpRequestMessage request = new HttpRequestMessage()
     //populate the request
     request.Content = stringContent;
     try
     {
        using (HttpResponseMessage response = await client
         .SendAsync(request, HttpCompletionOption.ResponseHeadersRead)
         .ConfigureAwait(false))
       {
          response.EnsureSuccessStatusCode();
          _lastRespose = await response.Content.ReadAsStringAsync();
          return _lastRespose;
       }
    }
    catch (Exception)
    { ... }

这很有效。我想让这段代码异步运行。所以我把它改成了获取任务,并使用ContinueWith在通话结束后获得回电

 private async void OnTestLoginCallCompleate(Task<HttpResponseMessage> response)
 {
     if (response.IsFaulted)
     {
         ShowErrorMessage();
         return;
     }
 }

    private void Login(Action<Task<HttpResponseMessage>> loginCallback)
    {
        _username = userNameTB.Text;
        _password = pwTB.Text;
        _url = urlTB.Text;

        if (String.IsNullOrEmpty(_username) ||
            String.IsNullOrEmpty(_password) ||
            String.IsNullOrEmpty(_url))
        {
            MessageBox.Show("All fields must not be empty", "Validation Error", MessageBoxButtons.OK);
        }

        HttpRequestMessage request = new HttpRequestMessage()
        {
            RequestUri = new Uri(_url),
            Method = HttpMethod.Post,
        };

        request.Headers.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
        String payload = "{ \"email\": \"" + _username + "\", \"password\": \"" + _password + "\" }";

        using (StringContent stringContent = new StringContent(payload, Encoding.UTF8, "application/json"))
        {
            request.Content = stringContent;
            client.SendAsync(request, HttpCompletionOption.ResponseContentRead).ContinueWith(loginCallback);
        }
    }

response.IsFaulted 是的。

0 回复 | 直到 5 年前

Itamar Kerbel 5 年前

正如在注释中提到的,问题来自于我用 using . 这将处理HttpResponseMessage,当它到达回调时,它已经被处理了。解决办法是移除 使用

private async void OnTestLoginCallCompleate(Task<HttpResponseMessage> response)
 {
     if (response.IsFaulted)
     {
         ShowErrorMessage();
         return;
     }
     HttpResponseMessage result = response.Result;
    ......code....
     result.Dispose();
 }

拆下使用部件并获得:

StringContent stringContent = new StringContent(payload, Encoding.UTF8, "application/json");
request.Content = stringContent;
client.SendAsync(request, HttpCompletionOption.ResponseContentRead).ContinueWith(loginCallback);

-2

Shahid 5 年前

通过查看代码,特别是这一部分:

using (StringContent stringContent = new StringContent(payload, Encoding.UTF8, "application/json"))
{
   request.Content = stringContent;
   client.SendAsync(request, HttpCompletionOption.ResponseContentRead).ContinueWith(OnTestLoginCallCompleate);
}

您需要添加等待 client.SendAsync 以便继续正常工作。

如果您尝试按以下方式修改代码,它应该可以工作。我已经在我的机器上进行了本地测试(稍加修改,所以运行正常)。

using (StringContent stringContent = new StringContent(payload, Encoding.UTF8, "application/json"))
{
   request.Content = stringContent;
   await client.SendAsync(request, HttpCompletionOption.ResponseContentRead).ContinueWith(OnTestLoginCallCompleate);
}