Question

I need to request values using functions in a DLL provided by the manufacturer of my particular piece of hardware (a weather station). I’m new to C#, and the concepts of delegates/events are tough to wrap my head around. Nonetheless, I’ve managed to pull the functions from the DLL and verify that data makes it through. My issue is with polling the instrument periodically with a Timer. In Initialize(), an object is instantiated, but the event isn’t handled leaving the object null. I’m out of ideas, and would like some advice!

public class HardwareData : EventArgs
{
    public float OutsideTemp { get; set; }
    public int OutsideHum { get; set; }
    public float WindSpeed { get; set; }
    public int WindDirection { get; set; }
}

public class Hardware : IDisposable
{
    private static Hardware v;
    private System.Timers.Timer hardwareTimer;
    private int counter = 0;
    private static readonly object padlock = new object();
    public static Hardware Instance
    {
        get
        {
            lock (padlock)
            {
                if (v == null)
                    v = new Hardware();
                return v;
            }
        }
    }

    public void Initialize()
    {
        try
        {
            hardwareTimer = new System.Timers.Timer(500);
            hardwareTimer.Elapsed += new ElapsedEventHandler(hardwareTimer_Elapsed);
            HardwareVue.OpenCommPort_V(3, 19200); //COM port and baud rate are verified.
            hardwareTimer.Start();
        }
        catch (Exception ex)
        {
            throw new InvalidOperationException("Unable to initialize.", ex);
        }
    }

    public HardwareData LastHardware { get; set; }

    void hardwareTimer_Elapsed(object sender, ElapsedEventArgs e)
    {
        try
        {
            counter += 1;
            Console.WriteLine(counter);
            HardwareVue.LoadCurrentHardwareData_V();
            HardwareData v = new HardwareData()
            {
                OutsideTemp = HardwareVue.GetOutsideTemp_V(),
                OutsideHum = HardwareVue.GetOutsideHumidity_V(),
                WindSpeed = HardwareVue.GetWindSpeed_V(),
                WindDirection = HardwareVue.GetWindDir_V()
            };
            LastHardware = v;
        }
        catch (Exception) { }
    }

    public void Dispose()
    {
        HardwareVue.CloseCommPort_V();
        hardwareTimer.Stop();
    }
}


[TestClass]
public class UnitTest1
{
    [TestMethod]
    public void TestMethod1()
    {
        Hardware test = new Hardware();
        try
        {
            if (test != null)
            {
                test.Initialize();
                test.Dispose();
                Assert.AreEqual(0, test.LastHardware.OutsideHum);
            }
        }
        catch (NullReferenceException ex)
        {
            Console.WriteLine("Object is null.");
        }
        // Console.WriteLine(test.LastHardware.OutsideHum);

    }
}

Answer 1

When working with timers, you need to enable the timer and make sure the events are rasied:

hardwareTimer.Enabled = true;
hardwareTimer.CanRaiseEvents = true;

For Reference: Timers on MSDN

Edit
In addition to the other comments to both the OP’s question and this answer, the issue with the LastHardware being null is due to the property never being instantiated before the timer initially fires. To resolve this, you should instantiate the LastHardware property in the default constructor (or in the Initialize method):

public Hardware()
{
  LastHardware = new HardwareData();
}

Of course, you’d want to set some default values upon instantiation.