C# Adding points to Chart in realtime

Question

I have got an question about adding points to charts.

My windows forms application is using a thread to get the Y value from another server. Every 500ms I get a new value(string) which should be added as a point, but I have no idea how to do that. It would be really nice if the points will be displayed in realtime and not only after ending the process. I think it is not a real difficult question but I didn`t find a solution.

Thread:

 private void Work()
    {
        int counter = 0;

        while (true)
        {
            counter++;
            WebClient code = new WebClient();
            speed_str = code.DownloadString("http://192.168.19.41/speedfile.html");
            speedval = Convert.ToDouble(speed_str);
            Console.WriteLine(speedval.ToString() + "\n Times executed: "  + counter);
            Thread.Sleep(1000);
        }
    }

Configuration and chart

 Thread thread = new Thread(new ThreadStart(this.Work));
        thread.IsBackground = true;
        thread.Name = "My Worker.";
        thread.Start();

        //Speed
        Series speed = new Series("Speed[m/s]");

        speed.ChartType = SeriesChartType.Spline;


        //Engines Left 
        engleft = new Series("Engines Left");

        engleft.ChartType = SeriesChartType.Spline;

        Engines.Series.Add(engleft);

        engleft.Points.Clear();

        string speed_read = Console.ReadLine();

Thanks for help :)

Which UI Framework are you using? (Please edit your post so that it will reflect that) — Eyal Perry, Jan 28 '17 at 12:38
It would also help if you post your code, so that users would see where you are stuck :) — Eyal Perry, Jan 28 '17 at 13:05
@EyalPerry I assume he is using Winforms and the native control element chartview... (in the tags) — 97hilfel, Jan 28 '17 at 13:05
I assume you tried adding items into the control from the background thread, got an exception and then just waited for the thread to finish before adding the whole bulk. If that is the case, I do have an answer for you. If not - please elaborate. — Eyal Perry, Jan 28 '17 at 13:08
@97hilfel Oh, sorry- I do not do WinForms so I had no idea :) PS, tags were added after my comment. — Eyal Perry, Jan 28 '17 at 13:08
I hope the added code will help a bit. I know it`s not the best but hopefully it`s possible to work with it :) — Tim B., Jan 28 '17 at 13:16

Eyal Perry · Accepted Answer · 2017-01-28T14:18:31.757

You have a classic Producer-Consumer scenario on your hands.

Which means that one thread produces an item (the background thread)
While another consumes it (the UI thread).

One way to communicate between a producer and a consumer is with an event :

    class Producer
    {

    public event EventHandler<double> YSeriesEvent;
    private Thread thread;

    public Producer()
    {
        thread = new Thread(new ThreadStart(this.Work));
        thread.IsBackground = true;
        thread.Name = "My Worker.";     
    }

    public void Start()
    {
        thread.Start();
    }

    private void Work()
    {
        int counter = 0;

        while (true)
        {
            counter++;
            WebClient code = new WebClient();
            speed_str = code.DownloadString("http://192.168.19.41/speedfile.html");
            speedval = Convert.ToDouble(speed_str);
            YSeriesEvent?.Invoke(this, speedval);
        }
    }
   }

Then, in your form you may do like so:

class MyForm : Form
{

private Producer producer;

public MyForm()
{
    producer = new Producer();
    producer.YSeriesEvent += MyHandler ;
    Load+= (sender, args) => producer.Start();
}

private void MyHandler(object o, double val)
{
    Invoke(new Action(() =>
    {
           //add value to chart here
    }));
}
}

Note that WinForms is single threaded, meaning that no thread can do work directly on a UI element, unless it is the UI thread.
This is why I called the Invoke method - it simply offloads work to be carried out on the UI thread.

C# Adding points to Chart in realtime

1 Answers1