Get DateTime.Now with milliseconds precision
How can I exactly construct a time stamp of actual time with milliseconds precision?
I need something like 16.4.2013 9:48:00:123. Is this possible? I have an application, where I sample values 10 times per second, and I need to show them in a graph.
Answer
How can I exactly construct a time stamp of actual time with milliseconds precision?
I suspect you mean millisecond accuracy. DateTime has a lot of precision, but is fairly coarse in terms of accuracy. Generally speaking, you can't. Usually the system clock (which is where DateTime.Now gets its data from) has a resolution of around 10-15 ms. See Eric Lippert's blog post about precision and accuracy for more details.
If you need more accurate timing than this, you may want to look into using an NTP client.
However, it's not clear that you really need millisecond accuracy here. If you don't care about the exact timing - you just want to show the samples in the right order, with "pretty good" accuracy, then the system clock should be fine. I'd advise you to use DateTime.UtcNow rather than DateTime.Now though, to avoid time zone issues around daylight saving transitions, etc.
If your question is actually just around converting a DateTime to a string with millisecond precision, I'd suggest using:
string timestamp = DateTime.UtcNow.ToString("yyyy-MM-dd HH:mm:ss.fff",
CultureInfo.InvariantCulture);
(Note that unlike your sample, this is sortable and less likely to cause confusion around whether it's meant to be "month/day/year" or "day/month/year".)