How Do I Store Laptimes In A Class And Database?

Wes is right, but it probably needs a little more explanation.

Use a DateTime in both the class and the database - and don't store the lap time, store the timestamp instead. That way, you aren't throwing any information away: you have the start time for teh race / lap, and the end time - you can then work out the elapsed time very simply when you need it, but you can also use it to order competitors, differentiate between races, and so forth. You may never have to, but there is no real overhead (datetime is stored internally as a long integer) and comparing / calculations are really easy. If you don't then you still need to store the start and a value to indicate the duration - which is probably in milliseconds anyway - plus it needs interpretation in order to be human readable.

Stopwatch.Elapsed Property[^] give you a TimeSpan value and you can use it as LapTime. Create TimeSpan in your class and set it.
you can save TimeSpan.Ticks[^] in your database by using bigint data type. TimeSpan.Ticks give you long value and you can convert it back to TimeSpan by using new TimeSpan(longValFromDb)[^]