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 => _period;
    public DateTime Next => _next;
    public TimeSpan DueTime => _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();
}