多个异步方法调用期间的异常处理不起作用

Question

我每秒生成超过 100 条消息，并在单独的线程中发送这些消息。当连接断开时，我想在调用者中捕获异常。由于我的所有消息都是异步发送的，因此我无法捕获异常。

这是调用dispatcherTimer_Tick方法的DispatcherTimer代码

dispatcherTimer = new DispatcherTimer();
dispatcherTimer.Interval = new TimeSpan(0, 0, 0, 1, 0);
dispatcherTimer.Tick += new EventHandler(dispatcherTimer_Tick);


private void dispatcherTimer_Tick(object sender, EventArgs e)
{
    try
    {
        item = "some generated message";
        Task.Run(() => SendMessage(item));                  
    }
    catch (Exception)
    {

    }
}

这是SendMessage 代码。我通过阅读基于：Async/Await - Best Practices in Asynchronous Programming 进行了更改，但它不起作用

private async static Task SendMessage(string message)
{
    try
    {
        (MQTT.RunAsync(message.ToString(), topic)).Wait();                
    }
    catch (Exception Ex)    
    {
        // Exceptions are not getting cought here
    }
}

MQTT.RunAsync 的定义

public static async Task RunAsync(string message)
{
    var mqttClient = factory.CreateMqttClient()               
    try
    {
        await mqttClient.ConnectAsync(options);
    }
    catch (Exception exception)
    {

    }
}

还有

Task<MqttClientConnectResult> ConnectAsync(IMqttClientOptions options)

更新问题

我的RunAsync 首先尝试连接，如果成功则发送消息。所以我不能在连接检查时写return。

 public Task RunAsync(string message, string topicName)
    {

            this.mqttClient.ConnectAsync(this.options);
            mqttClient.SubscribeAsync(new TopicFilterBuilder().WithTopic(this._topicname).WithExactlyOnceQoS().Build());
            var applicationMessage = new MqttApplicationMessageBuilder().WithTopic(this._topicname)
               .WithPayload(message).WithAtLeastOnceQoS().Build();

            if (stopSending == false)
            {
                return mqttClient.PublishAsync(applicationMessage);
            }
            return null;
    }

Answer 1

事件处理程序是允许async void 的例外

private async void dispatcherTimer_Tick(object sender, EventArgs e) {
    try {
        item = "some generated message";
        await SendMessage(item);
    } catch (Exception ex) {
        //...handle exception
    }
}

此外，您似乎正在以任何方式使用异常，因为它已经被进一步捕获到堆栈中。

尽量保持代码异步，不要混用像.Wait()或.Result这样的阻塞调用

private static Task SendMessage(string message) {
    return MQTT.RunAsync(message, topic);
}

public static async Task RunAsync(string message, string topicName) {
    await this.mqttClient.ConnectAsync(this.options);
    var topicFilter = new TopicFilterBuilder().WithTopic(this._topicname)
        .WithExactlyOnceQoS().Build();
    await mqttClient.SubscribeAsync(topicFilter);
    var applicationMessage = new MqttApplicationMessageBuilder().WithTopic(this._topicname)
       .WithPayload(message).WithAtLeastOnceQoS().Build();

    if (stopSending == false) {
        await mqttClient.PublishAsync(applicationMessage);
    }

}