c# async object

Question

I haven't really played with asyn operations before or multiple threads so this is all new to me. So I was hoping for some guidance

Suppose I have a class something like below

public class pinger
{


    // Constructor
    public Pinger()
    {
     do while exit = False;
    Uri url = new Uri("www.abhisheksur.com");
        string pingurl = string.Format("{0}", url.Host);
        string host = pingurl;
        bool result = false;
        Ping p = new Ping();
        try
        {
            PingReply reply = p.Send(host, 3000);
            if (reply.Status == IPStatus.Success)
                result = true;
        }
        catch { }
      //wait 2 seconds
      loop;
    }


}

so I can call this with

Pinger firstone = new Pinger

What I want if for control to then return to the main thread leaving the created instance running and pinging the host every two seconds and updating the result variable, that I can then use a get property when I want to know the status from the main thread.

Can any one suggest some good reading / examples to introduce me to multi threading in c#, using Ping as an example seemed a good easy thing to try this out with :)

Cheers

Aaron

Thorsten Dittmar · Accepted Answer · 2012-03-23 10:29:25Z

3

I can outline how the class should look :-)

public class pinger
{
    private Uri m_theUri;
    private Thread m_pingThread;
    private ManualResetEvent m_pingThreadShouldStop;

    private volatile bool m_lastPingResult = false;

    public Pinger(Uri theUri)
    {
        m_theUri = theUri;
    }


    public void Start()
    {
        if (m_pingThread == null)
        {
            m_pingThreadShouldStop = new ManualResetEvent(false);
            m_pingThread = new Thread(new ParameterizedThreadStart(DoPing));
            m_pingThread.Start(m_theUri);
        }
    }

    public void Stop()
    {
        if (m_pingThread !=  null)
        {
            m_pingThreadShouldStop.Set();
            m_pingThread.Join();

            m_pingThreadShouldStop.Close();
        }
    }


    public void DoPing(object state)
    {
        Uri myUri = state as Uri;
        while (!m_pingThreadShouldStop.WaitOne(50))
        {
            // Get the result for the ping
            ...

            // Set the property
            m_lastPingResult = pingResult;
        }
    }


    public bool LastPingResult
    {
        get { return m_lastPingResult; }
    }
}

What does it do? It is a new class with a Start and a Stop method. Start starts the ping, Stop stops the ping.

Pinging is done in a separate thread and with every ping, the result property is updated.

answered Mar 23, 2012 at 10:29

Thorsten Dittmar

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5 Comments

DevilWAH Over a year ago

How the hell you guys answer so quickly!! I will have a look at this in a bit and let you know :) but this looks very promising. I can understand the logic of programming, just wish I could learn and remember the syntax like you guys do!

Thorsten Dittmar Over a year ago

I'm not sure whether the syntax is 100% correct - you'll see when you paste this into Visual Studio :-) The longer you do stuff like that, the better you will remember how to do things.

DevilWAH Over a year ago

ManualResetEvent, ParameterizedThreadStart, Thread, I get "using directive or an assembly reference?" I have using System.Threading.Tasks; included but is there some thing else I am missing?

DevilWAH Over a year ago

Oh hold on it seem to be find if I add in (using System.Threading;)

DevilWAH Over a year ago

after one minor syntax issue ;) its working great this :) thank you for a very complete and easy to follow example.

MoonKnight · Accepted Answer · 2012-03-23 10:26:32Z

3

I would reccomend the Task Parallel Library (TPL) for this. A great article on using the TPL can be found here.

For other infomation on threading in C# can be found on Joseph Albahari's blog. This should provide all the information you need to get you started.

I hope this helps.

Edit: If you want an example of how to thread the above I will be happy to help.

answered Mar 23, 2012 at 10:26

MoonKnight

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1 Comment

DevilWAH Over a year ago

I will look them up chees, I would say yes to the offer of an example, but I think Thorsten's below has that wrapped up. :)

tmaj · Accepted Answer · 2016-12-22 01:12:48Z

I came up with a Task based approach where there are 3 code paths interacting - please note that most likely the work will be done with just one thread.

The output of the program shown further below is:

public class Program
{
    public static object _o = new object();
    public static void Main(string[] args)
    {
        PingReply pingResult = null;
        int i = 0;
        Task.Run(async () =>
        {
            var ii = 0;
            //no error handling, example only
            //no cancelling, example only 
            var ping = new System.Net.NetworkInformation.Ping();
            while (true)
            {
                Console.WriteLine($"A: {ii} > {DateTime.Now.TimeOfDay}");
                var localPingResult = await ping.SendPingAsync("duckduckgo.com");
                Console.WriteLine($"A: {ii} < {DateTime.Now.TimeOfDay}, status: {localPingResult?.Status}");
                lock (_o)
                {
                    i = ii;
                    pingResult = localPingResult;
                }

                await Task.Delay(1000);
                ii++;
            }
        });

        Task.Run(async () =>
        {
            //no error handling, example only 
            while (true)
            {
                await Task.Delay(2000);
                lock (_o)
                {
                    Console.WriteLine($"B: Checking at {DateTime.Now.TimeOfDay}, status no {i}: {pingResult?.Status}");
                }
            }
        });

        Console.WriteLine("This is the end of Main()");
        Console.ReadLine();
    }
}

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