Passing variables to timer event in a class

Question

I have a method in a class that receives and returns multiple parameters from/to Form1. I need to use a timed event to execute some code using those parameters. I have arranged this simplified code to show the dynamic:

class Motor
{
    public static System.Timers.Timer _timer;
    int valReg = 30;

    public void PID(decimal _actualSpeed, Decimal _speedRequest, out Decimal _pwmAuto, out decimal _preValReg)
    {

        _timer = new System.Timers.Timer();
        _timer.Interval = (3000);
        _timer.Elapsed += new System.Timers.ElapsedEventHandler(_timerAutoset);
        _timer.Enabled = true;
        // {....}
        _pwmAuto = valReg;
        _preValReg = valReg - 1;
    }
    static void _timerAutoset(object sender, System.Timers.ElapsedEventArgs e)
    {
        /* here I need to work with:
         _actualSpeed
         _speedRequest
         _pwmAuto
         _preValReg
        and send back the last two variables
         */
    }    
}

This is how I pass and receive the variables from Form1 button :

        private void button4_Click(object sender, EventArgs e)
        {
        // some code ................
        Motor mtr = new Motor();
        mtr.PID(speedRequest, actualSpeed, out pwmAuto, out xxx);
        //..more code

How can I pass/get back those parameters to/from _timerAutoset event?

Answer 1

I tend to solve this problem using anonymous delegates.

public void PID(decimal _actualSpeed, Decimal _speedRequest, out Decimal _pwmAuto, out decimal _preValReg)
{
    _pwmAuto = valReg;
    _preValReg = valReg - 1;

     // Because we cannot use [out] variables inside the anonymous degegates,
     // we make a value copy
     Decimal pwmAutoLocal = _pwmAuto;
     Decimal preValRegLocal = _preValReg;

    _timer = new System.Timers.Timer();
    _timer.Interval = (3000);
    _timer.Elapsed += (sender, e) => { HandleTimerElapsed(_actualSpeed, _speedRequst, pwmAutoLocal, preValRegLocal); };        
    _timer.Enabled = true;
    // {....}

}

static void HandleTimerElapsed(Decimal actualSpeed, Decimal speedRequst, Decimal pwmAuto, Decimal preValReg)
{
   // (...)
}

(You have to be mindful when the delegate accesses local variables from the enclosing block. Double-check the code to ensure the values stored in those variables will not change between the assignment of the event handler and the invocation of this handler).

Answer 2

It seems these parameters are coming from somewhere else. One approach could be to pass a callback via delegate and use it to get the updated values from.

Another approach will be to make a class and pass it to Motor's constructor and use its reference in the _timerAutoset to get the updated values.

Using Delegates:

class Motor
{
    public static System.Timers.Timer _timer;
    int valReg = 30;
    public delegate TimerParam ParameterizedTimerDelegate();
    public static ParameterizedTimerDelegate TimerCallback { get; set; }

    public void PID()
    {
        _timer = new System.Timers.Timer();
        _timer.Interval = (3000);
        _timer.Elapsed += new System.Timers.ElapsedEventHandler(_timerAutoset);
        _timer.Enabled = true;
        // {....}
        //Param.PwmAuto = valReg;
        //Param.PreValReg = valReg - 1;
    }
    static void _timerAutoset(object sender, System.Timers.ElapsedEventArgs e)
    {
        TimerParam param = TimerCallback();
        /* here you can use:
         Param.ActualSpeed
         Param.SpeedRequest
         Param.PwmAuto
         Param.PreValReg
        */
    }
}

Using a shared instance:

class TimerParam
{
    public decimal ActualSpeed { get; set; }
    public decimal SpeedRequest { get; set; }
    public Decimal PwmAuto { get; set; }
    public decimal PreValReg { get; set; }
}

class Motor
{
    public static System.Timers.Timer _timer;
    int valReg = 30;
    public TimerParam Param { get; set; }

    public void PID(TimerParam param)
    {
        Param = param;

        _timer = new System.Timers.Timer();
        _timer.Interval = (3000);
        _timer.Elapsed += new System.Timers.ElapsedEventHandler(_timerAutoset);
        _timer.Enabled = true;
        // {....}
        Param.PwmAuto = valReg;
        Param.PreValReg = valReg - 1;
    }
    static void _timerAutoset(object sender, System.Timers.ElapsedEventArgs e)
    {
        /* here you can use:
         Param.ActualSpeed
         Param.SpeedRequest
         Param.PwmAuto
         Param.PreValReg
        */
    }
}

You can then update the instance of TimerParam that you passed to the Motor class and timer will always get the updated values.

Answer 3

you could try using lambda expression for inserting additional arguement..

  _timer.Elapsed += (sender, e) => _timerAutoset(sender, e, _actualSpeed,_speedRequest);

your method be like

static void _timerAutoset(object sender, System.Timers.ElapsedEventArgs e,decimal speed,decimal speedRequest)