difference between Stopwatch.ElapsedMilliseconds and (stopDateTime - startDateTime).TotalMilliseconds

Question

I have:

Stopwatch stopWatch = new Stopwatch();
stopWatch.Start();

DateTime start  = DateTime.Now;
Thread.Sleep(5000);

stopWatch.Stop();
DateTime stop = DateTime.Now;

//stopWatch.ElapsedMilliseconds approximately equals to (stop - start).TotalMilliseconds

So is there a difference in these measurement methods?

Answer 1

From msdn, System.DateTime:

The Now property is frequently used to measure performance. However, because of its low resolution, it is not suitable for use as a benchmarking tool. A better alternative is to use the Stopwatch class.

Answer 2

Stopwatch is more precised than the calculation of (stop - start).TotalMilliseconds.

Check this post on SO.

Answer 3

Stopwatch uses/is a high performance counter which can measure one-hundredth of a millisecond if you don't query the integer ".Millisecond" property but the floating point ".Ellapsed.Totalmilliseconds" property.