System.Timers.Timer How to get the time remaining until Elapse

Question

Using C#, how may I get the time remaining (before the elapse event will occur) from a System.Timers.Timer object?

In other words, let say I set the timer interval to 6 hours, but 3 hours later, I want to know how much time is remaining. How would I get the timer object to reveal this time remaining?

Answer 1

The built-in timer doesn't provide the time remaining until elapse. You'll need to create your own class which wraps a timer and exposes this info.

Something like this should work.

public class TimerPlus : IDisposable
{
    private readonly TimerCallback _realCallback;
    private readonly Timer _timer;
    private TimeSpan _period;
    private DateTime _next;

    public TimerPlus(TimerCallback callback, object state, TimeSpan dueTime, TimeSpan period)
    {
        _timer = new Timer(Callback, state, dueTime, period);
        _realCallback = callback;
        _period = period;
        _next = DateTime.Now.Add(dueTime);
    }

    private void Callback(object state)
    {
        _next = DateTime.Now.Add(_period);
        _realCallback(state);
    }

    public TimeSpan Period
    {
        get
        {
            return _period;
        }
    }

    public DateTime Next
    {
        get
        {
            return _next;
        }
    }

    public TimeSpan DueTime
    {
        get
        {
            return _next - DateTime.Now;
        }
    }

    public bool Change(TimeSpan dueTime, TimeSpan period)
    {
        _period = period;
        _next = DateTime.Now.Add(dueTime);
        return _timer.Change(dueTime, period);
    }

    public void Dispose()
    {
        _timer.Dispose();
    }
}

Answer 2

I am aware, that the topic is more than 3 years old. However I came across it while tackling exactly the same problem.

Inspired by Samuel Neff, I came up with a WinForms-less solution by extending the standard System.Timers.Timer class:

    public class TimerPlus : System.Timers.Timer
    {
        private DateTime m_dueTime;

        public TimerPlus() : base()
        {
            this.Elapsed += this.ElapsedAction;
        }

        protected new void Dispose()
        {
            this.Elapsed -= this.ElapsedAction;
            base.Dispose();
        }

        public double TimeLeft
        {
            get
            {
                return (this.m_dueTime - DateTime.Now).TotalMilliseconds;
            }
        }

        public new void Start()
        {
            this.m_dueTime = DateTime.Now.AddMilliseconds(this.Interval);
            base.Start();
        }

        private void ElapsedAction(object sender, System.Timers.ElapsedEventArgs e)
        {
            if (this.AutoReset)
            {
                this.m_dueTime = DateTime.Now.AddMilliseconds(this.Interval);
            }
        }
    }

I hope it helps.

Answer 3

I guess the best method is to hold the start time in a variable and then calculate the elapsed time as

TimeSpan t = DateTime.Now - StartTime;