Java System.currentTimeMillis() equivalent in C#

Question

What is the equivalent of Java\'s System.currentTimeMillis() in C#?

Answer 1

We could also get a little fancy and do it as an extension method, so that it hangs off the DateTime class:

public static class DateTimeExtensions
{
    private static DateTime Jan1st1970 = new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);
    public static long currentTimeMillis(this DateTime d)
    {
        return (long) ((DateTime.UtcNow - Jan1st1970).TotalMilliseconds);
    }
}

Answer 2

If you want a timestamp to be compared between different processes, different languages (Java, C, C#), under GNU/Linux and Windows (Seven at least):

C#:

private static long nanoTime() {
   long nano = 10000L * Stopwatch.GetTimestamp();
   nano /= TimeSpan.TicksPerMillisecond;
   nano *= 100L;
   return nano;
}

Java:

java.lang.System.nanoTime();

C GNU/Linux:

static int64_t hpms_nano() {
   struct timespec t;
   clock_gettime( CLOCK_MONOTONIC, &t );
   int64_t nano = t.tv_sec;
   nano *= 1000;
   nano *= 1000;
   nano *= 1000;
   nano += t.tv_nsec;
   return nano;
}

C Windows:

static int64_t hpms_nano() {
   static LARGE_INTEGER ticksPerSecond;
   if( ticksPerSecond.QuadPart == 0 ) {
      QueryPerformanceFrequency( &ticksPerSecond );
   }
   LARGE_INTEGER ticks;
   QueryPerformanceCounter( &ticks );
   uint64_t nano = ( 1000*1000*10UL * ticks.QuadPart ) / ticksPerSecond.QuadPart;
   nano *= 100UL;
   return nano;
}

Answer 3

An alternative:

private static readonly DateTime Jan1st1970 = new DateTime
    (1970, 1, 1, 0, 0, 0, DateTimeKind.Utc);

public static long CurrentTimeMillis()
{
    return (long) (DateTime.UtcNow - Jan1st1970).TotalMilliseconds;
}

Answer 4

DateTimeOffset.UtcNow.ToUnixTimeMilliseconds()

Answer 5

If you are interested in TIMING, add a reference to System.Diagnostics and use a Stopwatch.

For example:

var sw = Stopwatch.StartNew();
...
var elapsedStage1 = sw.ElapsedMilliseconds;
...
var elapsedStage2 = sw.ElapsedMilliseconds;
...
sw.Stop();

Answer 6

The framework doesn't include the old seconds (or milliseconds) since 1970. The closest you get is DateTime.Ticks which is the number of 100-nanoseconds since january 1st 0001.