Why isn't my TimeSpan.Add() working?

问题

There has to be an easy answer:

var totalTime = TimeSpan.Zero;

foreach (var timesheet in timeSheets)
{
   //assume "time" is a correct, positive TimeSpan
   var time = timesheet.EndTime - timesheet.StartTime;
   totalTime.Add(time);
}

There's only one value in the list timeSheets and it is a positive TimeSpan (verified on local inspection).

回答1:

TimeSpans are value types. Try:

totalTime = totalTime.Add(time)

回答2:

This is a common mistake. TimeSpan.Add returns a new instance of TimeSpan.

回答3:

totalTime = totalTime.Add(time)

来源：https://stackoverflow.com/questions/3580947/why-isnt-my-timespan-add-working