Timestamps

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ValueStopwatch also exposes the timestamps it is built on. A timestamp is a long, so you can store it anywhere, for instance in an array or in a field updated with Interlocked, and compute durations later:

long start = ValueStopwatch.GetTimestamp();
// The operation to measure
long end = ValueStopwatch.GetTimestamp();

TimeSpan elapsed = ValueStopwatch.GetElapsedTime(start, end);
Assert.True(elapsed >= TimeSpan.Zero);

// The timestamps are ticks of Stopwatch.Frequency, so they can be stored and compared as numbers
Assert.Equal(TimeSpan.FromSeconds(1), ValueStopwatch.GetElapsedTime(0, Stopwatch.Frequency));

ValueStopwatch.GetTimestamp() returns the current value of the high-resolution counter, like Stopwatch.GetTimestamp().
ValueStopwatch.GetElapsedTime(startTimestamp, endTimestamp) converts the difference between two timestamps to a TimeSpan, using Stopwatch.Frequency, like Stopwatch.GetElapsedTime(startTimestamp, endTimestamp).

A timestamp counts ticks of Stopwatch.Frequency from an arbitrary origin. It only makes sense compared with another timestamp of the same machine: do not convert it to a date, and do not compare timestamps that come from different machines, or from before a restart of the machine.