C#中的DateTime
一、DateTime是值类型还是引用类型的探索
二、了解DateTime结构体
三、DateTime.Now和DateTime.UtcNow是怎么计算出来的
一、DateTime是值类型还是引用类型的探索
DateTime是值类型，因为DateTime是结构体，而结构体继承自System.ValueType，属于值类型
[Serializable, __DynamicallyInvokable]
public struct DateTime : IComparable, IFormattable, IConvertible, ISerializable, IComparable<DateTime>, IEquatable<DateTime>
{
// Fields
private ulong dateData;
private const string DateDataField = "dateData";
private const int DatePartDay = ;
private const int DatePartDayOfYear = ;
private const int DatePartMonth = ;
private const int DatePartYear = ;
private const int DaysPer100Years = 0x8eac;
private const int DaysPer400Years = 0x23ab1;
private const int DaysPer4Years = 0x5b5;
private const int DaysPerYear = 0x16d;
private const int DaysTo10000 = 0x37b9db;
private const int DaysTo1601 = 0x8eac4;
private const int DaysTo1899 = 0xa9559;
private static readonly int[] DaysToMonth365;
private static readonly int[] DaysToMonth366;
private const long DoubleDateOffset = 0x85103c0cb83c000L;
private const long FileTimeOffset = 0x701ce1722770000L;
private const ulong FlagsMask = 13835058055282163712L;
private const ulong KindLocal = 9223372036854775808L;
private const ulong KindLocalAmbiguousDst = 13835058055282163712L;
private const int KindShift = 0x3e;
private const ulong KindUnspecified = 0L;
private const ulong KindUtc = 0x4000000000000000L;
private const ulong LocalMask = 9223372036854775808L;
private const long MaxMillis = 0x11efae44cb400L;
internal const long MaxTicks = 0x2bca2875f4373fffL;
[__DynamicallyInvokable]
public static readonly DateTime MaxValue;
private const int MillisPerDay = 0x5265c00;
private const int MillisPerHour = 0x36ee80;
private const int MillisPerMinute = 0xea60;
private const int MillisPerSecond = 0x3e8;
internal const long MinTicks = 0L;
[__DynamicallyInvokable]
public static readonly DateTime MinValue;
private const double OADateMaxAsDouble = 2958466.0;
private const double OADateMinAsDouble = -657435.0;
private const long OADateMinAsTicks = 0x6efdddaec64000L;
private const long TicksCeiling = 0x4000000000000000L;
private const string TicksField = "ticks";
private const ulong TicksMask = 0x3fffffffffffffffL;
private const long TicksPerDay = 0xc92a69c000L;
private const long TicksPerHour = 0x861c46800L;
private const long TicksPerMillisecond = 0x2710L;
private const long TicksPerMinute = 0x23c34600L;
private const long TicksPerSecond = 0x989680L; // Methods
static DateTime();
[__DynamicallyInvokable]
public DateTime(long ticks);
[TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")]
private DateTime(ulong dateData);
[__DynamicallyInvokable]
public DateTime(long ticks, DateTimeKind kind);
private DateTime(SerializationInfo info, StreamingContext context);
[__DynamicallyInvokable]
public DateTime(int year, int month, int day);
internal DateTime(long ticks, DateTimeKind kind, bool isAmbiguousDst);
[TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")]
public DateTime(int year, int month, int day, Calendar calendar);
[__DynamicallyInvokable]
public DateTime(int year, int month, int day, int hour, int minute, int second);
[__DynamicallyInvokable]
public DateTime(int year, int month, int day, int hour, int minute, int second, DateTimeKind kind);
public DateTime(int year, int month, int day, int hour, int minute, int second, Calendar calendar);
[__DynamicallyInvokable]
public DateTime(int year, int month, int day, int hour, int minute, int second, int millisecond);
[__DynamicallyInvokable]
public DateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, DateTimeKind kind);
public DateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, Calendar calendar);
public DateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, Calendar calendar, DateTimeKind kind);
[__DynamicallyInvokable]
public DateTime Add(TimeSpan value);
private DateTime Add(double value, int scale);
[__DynamicallyInvokable, TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")]
public DateTime AddDays(double value);
[__DynamicallyInvokable, TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")]
public DateTime AddHours(double value);
[__DynamicallyInvokable, TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")]
public DateTime AddMilliseconds(double value);
[__DynamicallyInvokable, TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")]
public DateTime AddMinutes(double value);
[__DynamicallyInvokable]
public DateTime AddMonths(int months);
[__DynamicallyInvokable, TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")]
public DateTime AddSeconds(double value);
[__DynamicallyInvokable]
public DateTime AddTicks(long value);
[__DynamicallyInvokable]
public DateTime AddYears(int value);
[__DynamicallyInvokable]
public static int Compare(DateTime t1, DateTime t2);
[__DynamicallyInvokable]
public int CompareTo(DateTime value);
public int CompareTo(object value);
private static long DateToTicks(int year, int month, int day);
[__DynamicallyInvokable]
public static int DaysInMonth(int year, int month);
internal static long DoubleDateToTicks(double value);
[return: MarshalAs(UnmanagedType.Bool)]
[SecurityCritical, SuppressUnmanagedCodeSecurity, DllImport("QCall", CharSet=CharSet.Unicode)]
internal static extern bool EnableAmPmParseAdjustment();
[__DynamicallyInvokable]
public bool Equals(DateTime value);
[__DynamicallyInvokable]
public override bool Equals(object value);
[__DynamicallyInvokable]
public static bool Equals(DateTime t1, DateTime t2);
[__DynamicallyInvokable]
public static DateTime FromBinary(long dateData);
internal static DateTime FromBinaryRaw(long dateData);
[__DynamicallyInvokable]
public static DateTime FromFileTime(long fileTime);
[__DynamicallyInvokable]
public static DateTime FromFileTimeUtc(long fileTime);
[__DynamicallyInvokable]
public static DateTime FromOADate(double d);
private int GetDatePart(int part);
[__DynamicallyInvokable]
public string[] GetDateTimeFormats();
[__DynamicallyInvokable]
public string[] GetDateTimeFormats(char format);
[__DynamicallyInvokable]
public string[] GetDateTimeFormats(IFormatProvider provider);
[__DynamicallyInvokable]
public string[] GetDateTimeFormats(char format, IFormatProvider provider);
[TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries"), __DynamicallyInvokable]
public override int GetHashCode();
[MethodImpl(MethodImplOptions.InternalCall), SecurityCritical]
internal static extern long GetSystemTimeAsFileTime();
[TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
public TypeCode GetTypeCode();
internal bool IsAmbiguousDaylightSavingTime();
[__DynamicallyInvokable]
public bool IsDaylightSavingTime();
[__DynamicallyInvokable]
public static bool IsLeapYear(int year);
[__DynamicallyInvokable]
public static DateTime operator +(DateTime d, TimeSpan t);
[TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries"), __DynamicallyInvokable]
public static bool operator ==(DateTime d1, DateTime d2);
[TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries"), __DynamicallyInvokable]
public static bool operator >(DateTime t1, DateTime t2);
[TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries"), __DynamicallyInvokable]
public static bool operator >=(DateTime t1, DateTime t2);
[TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries"), __DynamicallyInvokable]
public static bool operator !=(DateTime d1, DateTime d2);
[TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries"), __DynamicallyInvokable]
public static bool operator <(DateTime t1, DateTime t2);
[TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries"), __DynamicallyInvokable]
public static bool operator <=(DateTime t1, DateTime t2);
[TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries"), __DynamicallyInvokable]
public static TimeSpan operator -(DateTime d1, DateTime d2);
[__DynamicallyInvokable]
public static DateTime operator -(DateTime d, TimeSpan t);
[__DynamicallyInvokable]
public static DateTime Parse(string s);
[__DynamicallyInvokable]
public static DateTime Parse(string s, IFormatProvider provider);
[__DynamicallyInvokable]
public static DateTime Parse(string s, IFormatProvider provider, DateTimeStyles styles);
[__DynamicallyInvokable]
public static DateTime ParseExact(string s, string format, IFormatProvider provider);
[__DynamicallyInvokable]
public static DateTime ParseExact(string s, string format, IFormatProvider provider, DateTimeStyles style);
[__DynamicallyInvokable]
public static DateTime ParseExact(string s, string[] formats, IFormatProvider provider, DateTimeStyles style);
[TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries"), __DynamicallyInvokable]
public static DateTime SpecifyKind(DateTime value, DateTimeKind kind);
[TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries"), __DynamicallyInvokable]
public TimeSpan Subtract(DateTime value);
[__DynamicallyInvokable]
public DateTime Subtract(TimeSpan value);
bool IConvertible.ToBoolean(IFormatProvider provider);
byte IConvertible.ToByte(IFormatProvider provider);
char IConvertible.ToChar(IFormatProvider provider);
[TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
DateTime IConvertible.ToDateTime(IFormatProvider provider);
decimal IConvertible.ToDecimal(IFormatProvider provider);
double IConvertible.ToDouble(IFormatProvider provider);
short IConvertible.ToInt16(IFormatProvider provider);
int IConvertible.ToInt32(IFormatProvider provider);
long IConvertible.ToInt64(IFormatProvider provider);
sbyte IConvertible.ToSByte(IFormatProvider provider);
float IConvertible.ToSingle(IFormatProvider provider);
object IConvertible.ToType(Type type, IFormatProvider provider);
ushort IConvertible.ToUInt16(IFormatProvider provider);
uint IConvertible.ToUInt32(IFormatProvider provider);
ulong IConvertible.ToUInt64(IFormatProvider provider);
[SecurityCritical]
void ISerializable.GetObjectData(SerializationInfo info, StreamingContext context);
private static double TicksToOADate(long value);
private static long TimeToTicks(int hour, int minute, int second);
[__DynamicallyInvokable]
public long ToBinary();
[TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")]
internal long ToBinaryRaw();
[__DynamicallyInvokable]
public long ToFileTime();
[__DynamicallyInvokable]
public long ToFileTimeUtc();
[__DynamicallyInvokable, TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")]
public DateTime ToLocalTime();
internal DateTime ToLocalTime(bool throwOnOverflow);
public string ToLongDateString();
public string ToLongTimeString();
[__DynamicallyInvokable]
public double ToOADate();
public string ToShortDateString();
public string ToShortTimeString();
[__DynamicallyInvokable]
public override string ToString();
[TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries"), __DynamicallyInvokable]
public string ToString(IFormatProvider provider);
[__DynamicallyInvokable]
public string ToString(string format);
[__DynamicallyInvokable]
public string ToString(string format, IFormatProvider provider);
[__DynamicallyInvokable]
public DateTime ToUniversalTime();
internal static bool TryCreate(int year, int month, int day, int hour, int minute, int second, int millisecond, out DateTime result);
[__DynamicallyInvokable]
public static bool TryParse(string s, out DateTime result);
[__DynamicallyInvokable]
public static bool TryParse(string s, IFormatProvider provider, DateTimeStyles styles, out DateTime result);
[__DynamicallyInvokable]
public static bool TryParseExact(string s, string format, IFormatProvider provider, DateTimeStyles style, out DateTime result);
[__DynamicallyInvokable]
public static bool TryParseExact(string s, string[] formats, IFormatProvider provider, DateTimeStyles style, out DateTime result); // Properties
[__DynamicallyInvokable]
public DateTime Date { [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries"), __DynamicallyInvokable] get; }
[__DynamicallyInvokable]
public int Day { [__DynamicallyInvokable, TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")] get; }
[__DynamicallyInvokable]
public DayOfWeek DayOfWeek { [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries"), __DynamicallyInvokable] get; }
[__DynamicallyInvokable]
public int DayOfYear { [__DynamicallyInvokable, TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")] get; }
[__DynamicallyInvokable]
public int Hour { [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries"), __DynamicallyInvokable] get; }
private ulong InternalKind { [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")] get; }
internal long InternalTicks { [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries")] get; }
[__DynamicallyInvokable]
public DateTimeKind Kind { [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries"), __DynamicallyInvokable] get; }
[__DynamicallyInvokable]
public int Millisecond { [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries"), __DynamicallyInvokable] get; }
[__DynamicallyInvokable]
public int Minute { [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries"), __DynamicallyInvokable] get; }
[__DynamicallyInvokable]
public int Month { [__DynamicallyInvokable, TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")] get; }
[__DynamicallyInvokable]
public static DateTime Now { [__DynamicallyInvokable] get; }
[__DynamicallyInvokable]
public int Second { [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries"), __DynamicallyInvokable] get; }
[__DynamicallyInvokable]
public long Ticks { [__DynamicallyInvokable, TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")] get; }
[__DynamicallyInvokable]
public TimeSpan TimeOfDay { [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries"), __DynamicallyInvokable] get; }
[__DynamicallyInvokable]
public static DateTime Today { [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries"), __DynamicallyInvokable] get; }
[__DynamicallyInvokable]
public static DateTime UtcNow { [TargetedPatchingOptOut("Performance critical to inline across NGen image boundaries"), SecuritySafeCritical, __DynamicallyInvokable] get; }
[__DynamicallyInvokable]
public int Year { [__DynamicallyInvokable, TargetedPatchingOptOut("Performance critical to inline this type of method across NGen image boundaries")] get; }
}
二、了解DateTime结构体
转到DateTime的定义，也可以看到DateTime确实是struct类型，
看来前面的试验都是无用功了，但DateTime到底是怎样的结构体呢，主要有如下成员
这些成员里面最关键的是Ticks
Ticks的时间值以 100 毫微秒为单位，它的64位中，前两位表示Kind，后面62位表示有多少个毫微秒。Kind用来指示 DateTime 结构是表示本地时间、协调通用时间 (UTC) 还是 UTC 和本地时间都未指定。Kind 字段用于处理本地时间和 UTC 时间之间的转换。
DateTime的值范围在0001/1/1 00:00:00到9999/12/31 23:59:59之间
三、DateTime.Now和DateTime.UtcNow是怎么计算出来的
反编译DateTime.Now如下：
[__DynamicallyInvokable]
public static DateTime Now
{
[__DynamicallyInvokable]
get
{
DateTime utcNow = UtcNow;
bool isAmbiguousLocalDst = false;
long ticks = TimeZoneInfo.GetDateTimeNowUtcOffsetFromUtc(utcNow, out isAmbiguousLocalDst).Ticks;
long num2 = utcNow.Ticks + ticks;
if (num2 > 0x2bca2875f4373fffL)
{
return new DateTime(0x2bca2875f4373fffL, DateTimeKind.Local);
}
if (num2 < 0L)
{
return new DateTime(0L, DateTimeKind.Local);
}
return new DateTime(num2, DateTimeKind.Local, isAmbiguousLocalDst);
}
}
大致的意思是先获取DateTime.UtcNow，然后转换为本地时间
再反编译DateTime.UtcNow：
[__DynamicallyInvokable]
public static DateTime UtcNow =>
new DateTime((ulong) ((GetSystemTimeAsFileTime() + 0x701ce1722770000L) | 0x4000000000000000L));
最后查阅GetSystemTimeAsFileTime()是Windows的API，作用便是获取当前的UTC时间
C#中的DateTime的更多相关文章
- sql语句中获取datetime的日期部分或时间部分
sql语句中获取datetime的日期部分 sql语句中 经常操作操作datetime类型数据.今天在写一个存储过程的时候需要将 一个datetime的值的 日期部分提取出来.网上有许多这方面的介绍. ...
- Dynamics AX 2012 R2 在AIF服务契约中使用DateTime
Reinhard在AIF中使用DateTime作为服务契约的参数,与DotNet程序进行交互时,总是因为时区的问题,导致DotNet提交的System.DateTime与AIF中接收的DateTime ...
- MySQL中的datetime与timestamp比较-------转载
原文地址http://database.51cto.com/art/200905/124240.htm MySQL中的datetime与timestamp比较 本文将通过实例比较MySQL中的date ...
- sql语句中获取datetime任何部分
sql语句中获取datetime的日期部分 sql语句中 经常操作操作datetime类型数据.今天在写一个存储过程的时候需要将 一个datetime的值的 日期部分提取出来.网上有许多这方面的介绍. ...
- SQL server数据库中的DateTime类型出现的问题
我们知道这个SQL server数据库中的DateTime类型是数据库应用开发中经经常使用到的一种数据类型.而C#语言中也有DateTime类型,尽管二者都是用来描写叙述时间的,可是它们的默认值是不同 ...
- SQL-27 给出每个员工每年薪水涨幅超过5000的员工编号emp_no、薪水变更开始日期from_date以及薪水涨幅值salary_growth，并按照salary_growth逆序排列。 提示：在sqlite中获取datetime时间对应的年份函数为strftime('%Y', to_date)
题目描述 给出每个员工每年薪水涨幅超过5000的员工编号emp_no.薪水变更开始日期from_date以及薪水涨幅值salary_growth,并按照salary_growth逆序排列. 提示:在s ...
- JS、C#及SQL中的DateTime
一:SQL中的DataTime 1. between and 相当于>= and <= 2. 常用的将DataTime查询成字符串的方法 Select CONVER ...
- .NET 中的DateTime
DateTime简介 DateTime是.NET中的时间类型,可以通过DateTime完成诸如获取当前的系统时间等操作.DateTime在.NET中是一个结构体,而并不是一个类. 如上图所示,这个图标 ...
- C＃中的DateTime：本周第一天，本月第一天，今年第一天，本周第一天的时间
有时辰需要按照当前时刻,断定其它的都没有什么难度,只是本季度稍稍麻烦些.因为一年有四个季度,可以按照当前月份,获得本季度第一个月的月份,然后这个月的第一天,就是本季度的第一天了 DateTime dt ...
- 关于C#中的DateTime类型的技巧
* datetime.now.tostring()方法默认的你是无法得到全部的时间的格式的,只能得到日期,得不到具体时间,如果要具体时间,就应该使用 datetime的tostring()重载,dat ...
随机推荐
- nginx的反向代理proxy_pass指令
1. 首先什么是代理服务器?客户机发送请求时,不会直接发送到目的主机,而是先被代理服务器收到,代理服务器收到客服机的请求后,再向目的机发出,目的机就会返回数据给客户机,在返回给客户机之前,会被代理服务 ...
- <转>大型分布式网站术语浅析
夜半睡起看书,看到一篇关于分布式网站性能优化术语的文章,个人觉得不错,分享出来... 原文地址:大型分布式网站术语分析 一.I/O优化 1.增加缓存,减少磁盘的访问次数. 2.优化磁盘的管理系统,设计 ...
- SkylineDemoForWeb JavaScript二次开发示例代码
SkylineDemoForWeb JavaScript二次开发示例代码 http://files.cnblogs.com/files/yitianhe/SkylineDemoForWeb.zip
- eclpse安装jetty插件
公司不用tomcat,使用的是jetty,那么学习一下如何在eclipse中安装jetty插件.
- [Oracle]In-Memory的Join Group 位于内存的何处？
In-Memory的Join Group 的数据字典位于内存的何处? 有客户问到,使用Oracle 的In-Memory功能时,如果用到了 Join Group,那么这些这些Join Group,位于 ...
- python3通过gevent.pool限制协程并发数量
协程虽然是轻量级的线程,但到达一定数量后,仍然会造成服务器崩溃出错.最好的方法通过限制协程并发数量来解决此类问题. server代码: #!/usr/bin/env python # -*- codi ...
- 程序员从技术开发到项目管理PM--思维转变
对以往所做项目的经验做下总结,作为项目经理首先要对项目负责,思维要做下转变,要从项目全局角度考虑问题: 从个人成就到团队成就. 无论是做管理还是做技术,成就导向意识是优秀员工的基本素质.只有具 ...
- Jenkins日常运维笔记-重启数据覆盖问题、迁移、基于java代码发版(maven构建)
之前在公司机房部署了一套jenkins环境,现需要迁移至IDC机房服务器上,迁移过程中记录了一些细节:1)jenkins默认的主目录放在当前用户家目录路径下的.jenkins目录中.如jenkins使 ...
- php类之clone 克隆
对象也能被“克隆” 在php5中,对象的传递方式默认为引用传递,如果我们想要在内存中生成两个一样的对象或者创建一个对象的副本,这时可以使用“克隆”. 通过 clone 克隆一个对象 对象的复制是通过关 ...
- C_数据结构_递归不同函数间调用
# include <stdio.h> void f(); void g(); void k(); void f() { printf("FFFF\n"); g(); ...