I need to implement time calculation for repository methods in my asp .net mvc project classes. The problem is that i need to send time calculation data to WCF Service which is time consuming. I think about threads which can help to cal WCF service asynchronously. But I have very little experience with it. Do I need to create new thread each time or I can create a global thread, if so then how? I have something like that:

StopWatch class

public class StopWatch
{
    private DateTime _startTime;
    private DateTime _endTime;

    public void Start()
    {
        _startTime = DateTime.Now;
    }
    protected void StopTimerAndWriteStatistics()
    {
        _endTime = DateTime.Now;
        TimeSpan timeResult = _endTime - _startTime;
        //WCF proxy object
        var reporting = AppServerUtility.GetProxy<IReporting>();
        //Send data to server
        reporting.WriteStatistics(_startTime, _endTime, timeResult, "some information");
    }

    public void Stop()
    {
        //Here is the thread I have question with
        var thread = new Thread(StopTimerAndWriteStatistics);
        thread.Start();
    }
}

Using of StopWatch class in Repository

public class SomeRepository
{
    public List<ObjectInfo> List()
    {
        StopWatch sw = new StopWatch();
        sw.Start();
        //performing long time operation
        sw.Stop();
    }
}

What am I doing wrong with threads?