取消令牌引发异常。无法捕获OperationCanceledException。我有用户未处理的

Question

我正在尝试使用取消令牌来取消HttpClient流，但是我无法处理“ OperationCanceledException”。它给了我“用户未处理的异常”。在过去的另一个项目中，相同的结构运行良好。还是有更好的方法来取消HttpClient流？谢谢。这是我的代码：

private async void Start_Click(object sender, RoutedEventArgs e)
{
    await DeserializeFromStream();
}
private void Cancel_Click(object sender, RoutedEventArgs e)
{
    cts.Cancel();
}
private async Task DeserializeFromStream()
{
    cts = new CancellationTokenSource();
    CancellationToken ct = cts.Token;
    try
    {
        using (var client = new HttpClient())

        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));
        client.DefaultRequestHeaders.Add("APP_VERSION", "1.0.0");
        client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", "tokentokentoken");
        using (var request = new HttpRequestMessage(HttpMethod.Get, "https://stream-fxpractice.oanda.com/v3/accounts/101-004-4455670-001/pricing/stream?instruments=EUR_USD"))
        using (var response = await client.SendAsync(request, HttpCompletionOption.ResponseHeadersRead, ct))
        {
            var Timeout = TimeSpan.FromMilliseconds(1000);

            response.EnsureSuccessStatusCode();
            if (response.IsSuccessStatusCode) { Console.WriteLine("\n success!"); } else { Console.WriteLine((int)response.StatusCode); }

            var stream = await response.Content.ReadAsStreamAsync();
            using (StreamReader sr = new StreamReader(stream))
            using (JsonTextReader reader = new JsonTextReader(sr))
            {
                reader.SupportMultipleContent = true;
                await Task.Run(() =>
                {
                    while (reader.Read())
                    {
                        if (reader.TokenType == JsonToken.StartObject)
                        {
                            // Load each object from the stream and do something with it
                            JObject obj = JObject.Load(reader);
                            if (obj["type"].ToString() == "PRICE")
                                Dispatcher.BeginInvoke((Action)(() => { debugOutput(obj["closeoutBid"].ToString()); }));
                        }

                        ct.ThrowIfCancellationRequested();
                    }

                }, ct);
            }
        }
    }
    catch (OperationCanceledException) // includes TaskCanceledException
    {
        MessageBox.Show("Your submission was canceled.");
    }
}

Answer 1

我相信您会看到“用户未处理的异常”，因为您正在调试器中运行它。要么：

• 单击Continue继续执行代码，或
• 不使用调试器运行代码。

这两个选项中的任何一个都将使OperationCanceledException被catch块捕获。