使用线程进行外部通信（PC-> RS485设备）

Question

I'm using NModbus4 to communicate over ModbusRTU (RS485). My program needs to continuously get data from a device, that device is disconnected and connected very often. While the device is disconnected I'm getting timeout exception (understandably) during witch the program is laggy (going through forms, pressing buttons etc.) since it waits sometime for the device to response.

Is it possible to move the Modbus connection to a separate thread to handle it parallel to user interface(or is there a better option)?

If so please help me with a simple example how to do it in connection with events (I'm passing device data and information through an event to display data).

Sample code:

    public MainGui()
    {
        InitializeComponent();
        DataTransport DataManagment = new DataTransport(); //DataTransport is a class that handles communication and publishes event 'DataSent'
        DataManagment.DataSent += new EventHandler<DataSentArgs>(UnpackData);
    }

    private void slaveDataReqTimer_Tick(object sender, EventArgs e)
    {
        //Timer that is responsible for fetching data
        new Thread(() =>
        {
            Thread.CurrentThread.IsBackground = true;
            DataManagment.RequestData();

        }).Start();
    }

    public void UnpackData(object sender, DataSentArgs e)
    {
        //Doing some stuff when data arrives
    }

The problem with this code is that I can't pass the event from new Thread to current Thread (additionally I don't know if the approach with threads is correct).

I'm just starting with C# and .NET so the sample code might not be in accordance with standard conventions - sorry for that.

Answer 1

Threads is a too low-level primitive for this - I would recommend to investigate tasks and avoid using threads in general as much as possible.

This is the code how it would look like in your case. The DataManagement.RequestData call happens on a different thread, taken from the thread pool, but right after that you get into the context of your primary thread again so you'll not have to perform any synchronization/marshaling/etc. If the ProcessData method is also slow, then you can do the same as with DataManagement.RequestData - perform it on a task. And again, no synchonization will be needed.

public MainWindow()
{
    InitializeComponent();

    var cts = new CancellationTokenSource();
    Unloaded += delegate { cts.Cancel(); };
    ProcessData(cts.Token);
}

async void ProcessData(CancellationToken ct)
{
    try
    {
        while (true)
        {
            ct.ThrowIfCancellationRequested();

            try
            {
                var dataItem = await Task.Run(() => DataManagement.RequestData());

                ProcessData(dataItem);
            }
            catch(Exception_Thrown_By_RequestData e)
            {
                // decide what do - either break the loop or continue if
                // this is not a heavy faiulre
            }

            await Task.Delay(DelayTime, ct);
        }
    }
    catch (TaskCanceledException) { }
    catch (OperationCanceledException) { }
}