How do I get from Stopwatch.GetTimestamp() to a DateTime?
Assume Stopwatch.IsHighResolution is true.
If it's a high resolution counter, there's no guarantee that the value has any correlation with the real time - for example, it may well be "ticks since the computer booted." For a non-high resolution timer, you could use new DateTime(Stopwatch.GetTimestamp()) but that won't necessarily give a useful value for a high resolution timer. (It certainly doesn't on my box.)
What are you trying to use this for? The idea of Stopwatch is to measure intervals of time.