多线程和侦听串行端口

Question

Lets say I want to receive some data from the serial port. Using a block call for serial.ReadLine() and using the following event.

private void port_DataReceived(object sender, System.IO.Ports.SerialDataReceivedEventArgs e)
{
        var port = (SerialPort)sender;

        string line = port.ReadLine();

            // PROCESS DATA Somewhere else

}

I was reading from different sources and all of they say that the serial.ReadLine has its own thread and I should not modify the UI from this thread unless using BeginInvoke. However, I notice that during some time the UI will become unresponsive anyway.

So here is my question. Calling a new thread inside port_DataReceived will be a bad idea? I want to receive the data and process the received data in another thread however mythread.Start() where to put it? I cannot be starting it all the time I just want it to know somehow when to run independently after receiving the data. And according to MSDN a aborted thread cannot be started again. Putting Thread.Sleep is freezing my UI.

Answer 1

You misunderstand what is going on. SerialPort.ReadLine() does not use a thread. It is your DataReceived event handler that runs on another thread. Necessary so that the SerialPort can notify your code about received data as quickly as possible without having to wait for your UI thread to go idle. Which does indeed mean that you cannot directly update your UI from your event handler, you'll get an InvalidOperationException when you try anyway.

The DataReceived event is certainly there to help you avoid freezing your UI. There are too few hints in your question to know what your real problem might be. One issue could be using Control.BeginInvoke() too often, flooding the UI thread with invoke requests so it doesn't get around to doing its regular duties. Like responding to input and painting. The workaround for that is to simply invoke less often, you only need to keep human eyes happy and they don't work that fast. Buffer the received data, keep the amount of output to your UI reasonable so a human can actually see more than a blur.

Another common issue is deadlock , it will permanently freeze your program. Easy to diagnose with a debugger, you'll see your program stuck on the SerialPort.Close() call. This happens when you use Control.Invoke() instead of Control.BeginInvoke(). Don't use Invoke().