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C#日期函數使用大全 DateTime 相關設定2 C#

隨手記 10月 16, 2011
C#日期函數使用大全
//今天
DateTime.Now.Date.ToShortDateString();
//昨天，就是今天的日期减一
DateTime.Now.AddDays(-1).ToShortDateString();
//明天，同理，加一
DateTime.Now.AddDays(1).ToShortDateString();
//本周(要知道本周的第一天就得先知道今天是星期几，从而得知本周的第一天就是几天前的那一天，
要注意的是这里的每一周是从周日始至周六止
DateTime.Now.AddDays(Convert.ToDouble((0 - Convert.ToInt16(DateTime.Now.DayOfWeek)))).ToShortDateString();
DateTime.Now.AddDays(Convert.ToDouble((6 - Convert.ToInt16(DateTime.Now.DayOfWeek)))).ToShortDateString();
//如果你还不明白，再看一下中文显示星期几的方法就应该懂了
//由于DayOfWeek返回的是数字的星期几，我们要把它转换成汉字方便我们阅读，有些人可能会用switch来一个一个地
对照，其实不用那么麻烦的
string[] Day = new string[] { "星期日", "星期一", "星期二", "星期三", "星期四", "星期五", "星期六" };
Day[Convert.ToInt16(DateTime.Now.DayOfWeek)];
//上周，同理，一个周是7天，上周就是本周再减去7天，下周也是一样
DateTime.Now.AddDays(Convert.ToDouble((0 - Convert.ToInt16(DateTime.Now.DayOfWeek))) - 7).ToShortDateString();
DateTime.Now.AddDays(Convert.ToDouble((6 - Convert.ToInt16(DateTime.Now.DayOfWeek))) - 7).ToShortDateString();
//下周
DateTime.Now.AddDays(Convert.ToDouble((0 - Convert.ToInt16(DateTime.Now.DayOfWeek))) + 7).ToShortDateString();
DateTime.Now.AddDays(Convert.ToDouble((6 - Convert.ToInt16(DateTime.Now.DayOfWeek))) + 7).ToShortDateString();
//本月,很多人都会说本月的第一天嘛肯定是1号，最后一天就是下个月一号再减一天。当然这是对的
//一般的写法
DateTime.Now.Year.ToString() + DateTime.Now.Month.ToString() + "1"; //第一天
DateTime.Parse(DateTime.Now.Year.ToString() + DateTime.Now.Month.ToString() + "1").AddMonths(1).AddDays(-1).ToShortDateString();//最后一天
//巧用C#里ToString的字符格式化更简便
DateTime.Now.ToString("yyyy-MM-01");
DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(1).AddDays(-1).ToShortDateString();
//上个月，减去一个月份
DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(-1).ToShortDateString();
DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddDays(-1).ToShortDateString();
//下个月，加去一个月份
DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(1).ToShortDateString();
DateTime.Parse(DateTime.Now.ToString("yyyy-MM-01")).AddMonths(2).AddDays(-1).ToShortDateString();
//7天后
DateTime.Now.Date.ToShortDateString();
DateTime.Now.AddDays(7).ToShortDateString();
//7天前
DateTime.Now.AddDays(-7).ToShortDateString();
DateTime.Now.Date.ToShortDateString();
//本年度，用ToString的字符格式化我们也很容易地算出本年度的第一天和最后一天
DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).ToShortDateString();
DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(1).AddDays(-1).ToShortDateString();
//上年度，不用再解释了吧
DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(-1).ToShortDateString();
DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddDays(-1).ToShortDateString();
//下年度
DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(1).ToShortDateString();
DateTime.Parse(DateTime.Now.ToString("yyyy-01-01")).AddYears(2).AddDays(-1).ToShortDateString();
//本季度，很多人都会觉得这里难点，需要写个长长的过程来判断。其实不用的，我们都知道一年四个季度，一个季度三个月
//首先我们先把日期推到本季度第一个月，然后这个月的第一天就是本季度的第一天了
DateTime.Now.AddMonths(0 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01");
//同理，本季度的最后一天就是下季度的第一天减一
DateTime.Parse(DateTime.Now.AddMonths(3 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01")).AddDays(-1).ToShortDateString();
//下季度
DateTime.Now.AddMonths(3 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01");
DateTime.Parse(DateTime.Now.AddMonths(6 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01")).AddDays(-1).ToShortDateString();
//上季度
DateTime.Now.AddMonths(-3 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01");
DateTime.Parse(DateTime.Now.AddMonths(0 - ((DateTime.Now.Month - 1) % 3)).ToString("yyyy-MM-01")).AddDays(-1).ToShortDateString();
//如何获得当月有多少天
int m=System.DateTime.DaysInMonth(System.DateTime.Now.Year,System.DateTime.Now.Month);
//获取某月的实际工作日(即不包括周六日)
//调用
//int days =getDays(System.DateTime.Now));
private int getDays(System.DateTime date1)
{
int m=System.DateTime.DaysInMonth(date1.Year,date1.Month);
int mm=0;
for(int i=1;i<=m;i++)
{
System.DateTime date=Convert.ToDateTime(date1.Year+"-"+date1.Month+"-"+i);
switch (date.DayOfWeek)
{
case System.DayOfWeek.Monday:
case System.DayOfWeek.Thursday:
case System.DayOfWeek.Tuesday:
case System.DayOfWeek.Wednesday:
case System.DayOfWeek.Friday:
mm=mm+1;
break;
}
}
return mm;
}
获得任意两日期之间的有效工作日(不包括周六日) 获得任意两日期之间的有效工作日(不包括周六日)#region 获得任意两日期之间的有效工作日(不包括周六日)
//调用
//DateTime date1=Convert.ToDateTime("2005-10-20");
//DateTime date2=Convert.ToDateTime("2005-11-01");
//int days =getDays(date1,date2);
private int getDays(System.DateTime date1,System.DateTime date2)
{
string m=DateDiff(EnumDateCompare.day,date1,date2).ToString("f0");
int mm=0;
for(int i=0;i<=Convert.ToInt32(m);i++)
{
System.DateTime date=Convert.ToDateTime(date1.AddDays(i));
switch (date.DayOfWeek)
{
case System.DayOfWeek.Monday:
case System.DayOfWeek.Thursday:
case System.DayOfWeek.Tuesday:
case System.DayOfWeek.Wednesday:
case System.DayOfWeek.Friday:
mm=mm+1;
break;
}
}
return mm;
}
#endregion
格式输出
格式输出#region 格式输出
private void Page_Load(object sender, System.EventArgs e)
{
System.Globalization.DateTimeFormatInfo myDTFI = new System.Globalization.CultureInfo( "en-US", false ).DateTimeFormat;
//中国用zh-cn
DateTime myDT =System.DateTime.Now;
Response.Write(myDT.ToString("f",myDTFI));
/**//**//**//*
This code produces the following output.
FORMAT en-US EXAMPLE
CHAR VALUE OF ASSOCIATED PROPERTY, IF ANY
d 1/3/2002 M/d/yyyy (ShortDatePattern)
D Thursday, January 03, 2002 dddd, MMMM dd, yyyy (LongDatePattern)
f Thursday, January 03, 2002 12:00 AM
F Thursday, January 03, 2002 12:00:00 AM dddd, MMMM dd, yyyy h:mm:ss tt (FullDateTimePattern)
g 1/3/2002 12:00 AM
G 1/3/2002 12:00:00 AM
m January 03 MMMM dd (MonthDayPattern)
M January 03 MMMM dd (MonthDayPattern)
r Thu, 03 Jan 2002 00:00:00 GMT ddd, dd MMM yyyy HH':'mm':'ss 'GMT' (RFC1123Pattern)
R Thu, 03 Jan 2002 00:00:00 GMT ddd, dd MMM yyyy HH':'mm':'ss 'GMT' (RFC1123Pattern)
s 2002-01-03T00:00:00 yyyy'-'MM'-'dd'T'HH':'mm':'ss (SortableDateTimePattern)
t 12:00 AM h:mm tt (ShortTimePattern)
T 12:00:00 AM h:mm:ss tt (LongTimePattern)
u 2002-01-03 00:00:00Z yyyy'-'MM'-'dd HH':'mm':'ss'Z' (UniversalSortableDateTimePattern)
U Thursday, January 03, 2002 8:00:00 AM
y January, 2002 MMMM, yyyy (YearMonthPattern)
Y January, 2002 MMMM, yyyy (YearMonthPattern)
*/
}
#endregion
获得本周的周六和周日
ConvertDateToWeek#region ConvertDateToWeek
public static void ConvertDateToWeek(DateTime date,out DateTime firstdate,out DateTime lastdate)
{
DateTime first=System.DateTime.Now;
DateTime last=System.DateTime.Now;
switch (date.DayOfWeek)
{ case System.DayOfWeek.Monday:
first=date.AddDays(-1);
last=date.AddDays(5);
break;
case System.DayOfWeek.Tuesday:
first=date.AddDays(-2);
last=date.AddDays(4);
break;
case System.DayOfWeek.Wednesday:
first=date.AddDays(-3);
last=date.AddDays(3);
break;
case System.DayOfWeek.Thursday:
first=date.AddDays(-4);
last=date.AddDays(2);
break;
case System.DayOfWeek.Friday:
first=date.AddDays(-5);
last=date.AddDays(1);
break;
case System.DayOfWeek.Saturday:
first=date.AddDays(-6);
last=date;
break;
case System.DayOfWeek.Sunday:
first=date;
last=date.AddDays(6);
break;
}
firstdate=first;
lastdate=last;
}
#endregion
//调用
DateTime firstdate=System.DateTime.Now;
DateTime lastdate=System.DateTime.Now;
ConvertDateToWeek(date,out firstdate,out lastdate);
獲得當前日期是該年度的第幾周
DateTime dt = Convert.ToDateTime("2006-05-01");
int weeks = dt.DayOfYear / 7 + 1;
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