C＃中的Java System.currentTimeMillis（）等效

Question

在C＃中，Java的System.currentTimeMillis()相当于什么？

Answer 1

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 2

A common idiom in Java is to use the currentTimeMillis() for timing or scheduling purposes, where you're not interested in the actual milliseconds since 1970, but instead calculate some relative value and compare later invocations of currentTimeMillis() to that value.

If that's what you're looking for, the C# equivalent is Environment.TickCount .

Answer 3

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 4

the System.currentTimeMillis() in java returns the current time in milliseconds from 1/1/1970

c# that would be

public static double GetCurrentMilli()
    {
        DateTime Jan1970 = new DateTime(1970, 1, 1, 0, 0,0,DateTimeKind.Utc);
        TimeSpan javaSpan = DateTime.UtcNow - Jan1970;
        return javaSpan.TotalMilliseconds;
    }

edit: made it utc as suggested :)

Answer 5

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 6

Here is a simple way to approximate the Unix timestamp. Using UTC is closer to the unix concept, and you need to covert from double to long .

TimeSpan ts = (DateTime.UtcNow - new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc));
long millis = (long)ts.TotalMilliseconds;
Console.WriteLine("millis={0}", millis);

prints:

millis=1226674125796

Answer 7

DateTimeOffset.UtcNow.ToUnixTimeMilliseconds()

Answer 8

我只是考虑如何实现你一直在努力的最直接的方式如下：

DateTime.Now.Ticks / TimeSpan.TicksPerMillisecond

Answer 9

该框架不包括自1970年以来的旧秒（或毫秒）。您得到的最接近的是DateTime.Ticks，它是自0001年1月1日以来100纳秒的数量。

Answer 10

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 11

I know question asks for equivalent but since I use those 2 for the same tasks I throw in GetTickCount . I might be nostalgic but System.currentTimeMillis() and GetTickCount() are the only ones I use for getting ticks.

[DllImport("kernel32.dll")]
static extern uint GetTickCount();

// call
uint ticks = GetTickCount();