Start a stopwatch from specified time

Question

Im trying to start a stopwatch from a given time (decimal value pulled from a database). However, because the Stopwatch.Elapsed.Add returns a new timespan rather than modify

Answer 1

The normal StopWatch does not support initialization with an offset timespan and TimeSpan is a struct, therefore Elapsed is immutable. You could write a wrapper around StopWatch:

public class StopWatchWithOffset
{
    private Stopwatch _stopwatch = null;
    TimeSpan _offsetTimeSpan;

    public StopWatchWithOffset(TimeSpan offsetElapsedTimeSpan)
    {
        _offsetTimeSpan = offsetElapsedTimeSpan;
        _stopwatch = new Stopwatch();
    }

    public void Start()
    {
        _stopwatch.Start();
    }

    public void Stop()
    {
        _stopwatch.Stop();
    }

    public TimeSpan ElapsedTimeSpan
    {
        get
        {
            return _stopwatch.Elapsed + _offsetTimeSpan;
        }
        set
        {
            _offsetTimeSpan = value;
        }
    }
}

Now you can add a start-timespan:

var offsetTimeStamp = TimeSpan.FromHours(1);
var watch = new StopWatchWithOffset(offsetTimeStamp);
watch.Start();
System.Threading.Thread.Sleep(300); 
Console.WriteLine(watch.ElapsedTimeSpan);// 01:00:00.2995983