C# 如何截断 .NET DateTime 的毫秒数

How to truncate milliseconds off of a .NET DateTime

提问by Jeff Putz

I'm trying to compare a time stamp from an incoming request to a database stored value. SQL Server of course keeps some precision of milliseconds on the time, and when read into a .NET DateTime, it includes those milliseconds. The incoming request to the system, however, does not offer that precision, so I need to simply drop the milliseconds.

我正在尝试将来自传入请求的时间戳与数据库存储值进行比较。SQL Server 当然在时间上保持一定的毫秒精度，当读入 .NET DateTime 时，它​​包括这些毫秒。然而，系统的传入请求并没有提供这种精度，所以我需要简单地删除毫秒。

I feel like I'm missing something obvious, but I haven't found an elegant way to do it (C#).

我觉得我错过了一些明显的东西，但我还没有找到一种优雅的方法来做到这一点（C#）。

采纳答案by Joe

The following will work for a DateTime that has fractional milliseconds, and also preserves the Kind property (Local, Utc or Undefined).

以下内容适用于具有小数毫秒的 DateTime，并且还保留了 Kind 属性（Local、Utc 或 Undefined）。

DateTime dateTime = ... anything ...
dateTime = new DateTime(
    dateTime.Ticks - (dateTime.Ticks % TimeSpan.TicksPerSecond), 
    dateTime.Kind
    );

or the equivalent and shorter:

或等效且更短的：

dateTime = dateTime.AddTicks( - (dateTime.Ticks % TimeSpan.TicksPerSecond));

This could be generalized into an extension method:

这可以推广为一个扩展方法：

public static DateTime Truncate(this DateTime dateTime, TimeSpan timeSpan)
{
    if (timeSpan == TimeSpan.Zero) return dateTime; // Or could throw an ArgumentException
    if (dateTime == DateTime.MinValue || dateTime == DateTime.MaxValue) return dateTime; // do not modify "guard" values
    return dateTime.AddTicks(-(dateTime.Ticks % timeSpan.Ticks));
}

which is used as follows:

其用法如下：

dateTime = dateTime.Truncate(TimeSpan.FromMilliseconds(1)); // Truncate to whole ms
dateTime = dateTime.Truncate(TimeSpan.FromSeconds(1)); // Truncate to whole second
dateTime = dateTime.Truncate(TimeSpan.FromMinutes(1)); // Truncate to whole minute
...

回答by chris.w.mclean

DateTime d = DateTime.Now;
d = d.AddMilliseconds(-d.Millisecond);

回答by benPearce

var date = DateTime.Now;

date = new DateTime(date.Year, date.Month, date.Day, date.Hour, date.Minute, date.Second, date.Kind);

回答by Bob

Instead of dropping the milliseconds then comparing, why not compare the difference?

与其放弃毫秒然后比较，为什么不比较差异呢？

DateTime x; DateTime y;
bool areEqual = (x-y).TotalSeconds == 0;

or

或者

TimeSpan precision = TimeSpan.FromSeconds(1);
bool areEqual = (x-y).Duration() < precision;

回答by Diadistis

Less obvious but more than 2 times faster :

不太明显，但快了 2 倍以上：

// 10000000 runs

DateTime d = DateTime.Now;

// 484,375ms
d = new DateTime((d.Ticks / TimeSpan.TicksPerSecond) * TimeSpan.TicksPerSecond);

// 1296,875ms
d = d.AddMilliseconds(-d.Millisecond);

回答by Joe

Regarding Diadistis response. This worked for me, except I had to use Floor to remove the fractional part of the division before the multiplication. So,

关于 Diadistis 的反应。这对我有用，除了我必须在乘法之前使用 Floor 删除除法的小数部分。所以，

d = new DateTime((d.Ticks / TimeSpan.TicksPerSecond) * TimeSpan.TicksPerSecond);

becomes

变成

d = new DateTime(Math.Floor(d.Ticks / TimeSpan.TicksPerSecond) * TimeSpan.TicksPerSecond);

I would have expected the division of two Long values to result in a Long, thus removing the decimal part, but it resolves it as a Double leaving the exact same value after the multiplication.

我原以为两个 Long 值的除法会产生一个 Long，从而删除小数部分，但它将其解析为 Double ，在乘法后留下完全相同的值。

Eppsy

爱普西

回答by Sky Sanders

Here is an extension method based on a previous answer that will let you truncate to any resolution...

这是基于先前答案的扩展方法，可让您截断为任何分辨率...

Usage:

用法：

DateTime myDateSansMilliseconds = myDate.Truncate(TimeSpan.TicksPerSecond);
DateTime myDateSansSeconds = myDate.Truncate(TimeSpan.TicksPerMinute)

Class:

班级：

public static class DateTimeUtils
{
    /// <summary>
    /// <para>Truncates a DateTime to a specified resolution.</para>
    /// <para>A convenient source for resolution is TimeSpan.TicksPerXXXX constants.</para>
    /// </summary>
    /// <param name="date">The DateTime object to truncate</param>
    /// <param name="resolution">e.g. to round to nearest second, TimeSpan.TicksPerSecond</param>
    /// <returns>Truncated DateTime</returns>
    public static DateTime Truncate(this DateTime date, long resolution)
    {
        return new DateTime(date.Ticks - (date.Ticks % resolution), date.Kind);
    }
}

回答by HerbalMart

2 Extension methods for the solutions mentioned above

2 上述解决方案的扩展方法

    public static bool LiesAfterIgnoringMilliseconds(this DateTime theDate, DateTime compareDate, DateTimeKind kind)
    {
        DateTime thisDate = new DateTime(theDate.Year, theDate.Month, theDate.Day, theDate.Hour, theDate.Minute, theDate.Second, kind);
        compareDate = new DateTime(compareDate.Year, compareDate.Month, compareDate.Day, compareDate.Hour, compareDate.Minute, compareDate.Second, kind);

        return thisDate > compareDate;
    }


    public static bool LiesAfterOrEqualsIgnoringMilliseconds(this DateTime theDate, DateTime compareDate, DateTimeKind kind)
    {
        DateTime thisDate = new DateTime(theDate.Year, theDate.Month, theDate.Day, theDate.Hour, theDate.Minute, theDate.Second, kind);
        compareDate = new DateTime(compareDate.Year, compareDate.Month, compareDate.Day, compareDate.Hour, compareDate.Minute, compareDate.Second, kind);

        return thisDate >= compareDate;
    }

usage:

用法：

bool liesAfter = myObject.DateProperty.LiesAfterOrEqualsIgnoringMilliseconds(startDateTime, DateTimeKind.Utc);

回答by KingPong

Sometimes you want to truncate to something calendar-based, like year or month. Here's an extension method that lets you choose any resolution.

有时你想截断到基于日历的东西，比如年或月。这是一种扩展方法，可让您选择任何分辨率。

public enum DateTimeResolution
{
    Year, Month, Day, Hour, Minute, Second, Millisecond, Tick
}

public static DateTime Truncate(this DateTime self, DateTimeResolution resolution = DateTimeResolution.Second)
{
    switch (resolution)
    {
        case DateTimeResolution.Year:
            return new DateTime(self.Year, 1, 1, 0, 0, 0, 0, self.Kind);
        case DateTimeResolution.Month:
            return new DateTime(self.Year, self.Month, 1, 0, 0, 0, self.Kind);
        case DateTimeResolution.Day:
            return new DateTime(self.Year, self.Month, self.Day, 0, 0, 0, self.Kind);
        case DateTimeResolution.Hour:
            return self.AddTicks(-(self.Ticks % TimeSpan.TicksPerHour));
        case DateTimeResolution.Minute:
            return self.AddTicks(-(self.Ticks % TimeSpan.TicksPerMinute));
        case DateTimeResolution.Second:
            return self.AddTicks(-(self.Ticks % TimeSpan.TicksPerSecond));
        case DateTimeResolution.Millisecond:
            return self.AddTicks(-(self.Ticks % TimeSpan.TicksPerMillisecond));
        case DateTimeResolution.Tick:
            return self.AddTicks(0);
        default:
            throw new ArgumentException("unrecognized resolution", "resolution");
    }
}

回答by Sergio Cabral

A way for easy reading is...

一种轻松阅读的方法是...

//Remove milliseconds
DateTime date = DateTime.Now;
date = DateTime.ParseExact(date.ToString("yyyy-MM-dd HH:mm:ss"), "yyyy-MM-dd HH:mm:ss", null);

And more...

和更多...

//Remove seconds
DateTime date = DateTime.Now;
date = DateTime.ParseExact(date.ToString("yyyy-MM-dd HH:mm"), "yyyy-MM-dd HH:mm", null);

//Remove minutes
DateTime date = DateTime.Now;
date = DateTime.ParseExact(date.ToString("yyyy-MM-dd HH"), "yyyy-MM-dd HH", null);

//and go on...