C#根据当前时间确定日期范围（本周、本月、本季度、本年度及常见日期方法荟萃

DateTime dt = DateTime.Now;  //当前时间

DateTime startWeek = dt.AddDays(1 - Convert.ToInt32(dt.DayOfWeek.ToString("d")));  //本周周一
DateTime endWeek = startWeek.AddDays(6);  //本周周日

DateTime startMonth = dt.AddDays(1 - dt.Day);  //本月月初
DateTime endMonth = startMonth.AddMonths(1).AddDays(-1);  //本月月末
//DateTime endMonth = startMonth.AddDays((dt.AddMonths(1) - dt).Days - 1);  //本月月末

DateTime startQuarter = dt.AddMonths(0 - (dt.Month - 1) % 3).AddDays(1 - dt.Day);  //本季度初
DateTime endQuarter = startQuarter.AddMonths(3).AddDays(-1);  //本季度末

DateTime startYear = new DateTime(dt.Year, 1, 1);  //本年年初
DateTime endYear = new DateTime(dt.Year, 12, 31);  //本年年末

昨天、明天、上周、上月、上季度、上年度等等，只要AddDays()、AddMonths()、AddYears()这几种方法组合

一.如何获得当月有多少天
int m=System.DateTime.DaysInMonth(System.DateTime.Now.Year,System.DateTime.Now.Month);二.日期型格式处理通用方法
1.在webconfig中配置如下
<add key="ShortDatePattern" value="MM-dd-yyyy" />
<add key="LongDatePattern" value="dddd-MMMM dd-yyyy" />
<add key="ShortTimePattern" value="hh:mm tt" />
<add key="LongTimePattern" value="hh:mm tt" />2.在global.asax中
protected void Application_BeginRequest(Object sender, EventArgs e)
{
Thread currentThread = Thread.CurrentThread;
CultureInfo cul = currentThread.CurrentCulture.Clone() as CultureInfo;
cul.DateTimeFormat.ShortDatePattern= BLLFacade.Common.GetShortDatePattern();
cul.DateTimeFormat.LongDatePattern= BLLFacade.Common.GetLongDatePattern();
cul.DateTimeFormat.ShortTimePattern= BLLFacade.Common.GetShortTimePattern();
cul.DateTimeFormat.LongTimePattern= BLLFacade.Common.GetLongTimePattern();
currentThread.CurrentCulture = cul;
}3.在业务逻辑层中
public static string GetShortDatePattern()
{
return System.Configuration.ConfigurationSettings.AppSettings["ShortDatePattern"];
}

public static string GetLongDatePattern()
{
return System.Configuration.ConfigurationSettings.AppSettings["LongDatePattern"];
}

public static string GetShortTimePattern()
{
return System.Configuration.ConfigurationSettings.AppSettings["ShortTimePattern"];
}

public static string GetLongTimePattern()
{
return System.Configuration.ConfigurationSettings.AppSettings["LongTimePattern"];
}4.然后在其他地方正常调用就可以了，如果需要修改格式只需要修改webconfig中的，且可以保证整个系统中的所有格式都是一致的
三.在asp.net中怎么样计算两个日期相差的年、月份、日期、小时、分钟 、妙等
在asp.net中怎么样计算两个日期相差的年、月份、日期、小时、分钟 、妙等#region 在asp.net中怎么样计算两个日期相差的年、月份、日期、小时、分钟 、妙等
//        调用
//        DateTime a=Convert.ToDateTime("2005-09-03 20:15");
//        DateTime b=Convert.ToDateTime("2005-09-04 09:09 ");
//        double d=Bll.Common.DateDiff(Bll.Common.EnumDateCompare.day,a,b);
//        Response.Write(d.ToString("f0"));//四舍五入
        public enum EnumDateCompare
        {
            year    =1,
            month    =2,
            day        =3,
            hour    =4,
            minute    =5,
            second    =6
        }
        public static double DateDiff(EnumDateCompare howtocompare, System.DateTime startDate, System.DateTime endDate)
        {
            double diff=0;
            System.TimeSpan TS = new System.TimeSpan(endDate.Ticks-startDate.Ticks);

            switch (howtocompare)
            {
                case EnumDateCompare.year:
                    diff = Convert.ToDouble(TS.TotalDays/365);
                    break;
                case EnumDateCompare.month:
                    diff = Convert.ToDouble((TS.TotalDays/365)*12);
                    break;
                case EnumDateCompare.day:
                    diff = Convert.ToDouble(TS.TotalDays);
                    break;
                case EnumDateCompare.hour:
                    diff = Convert.ToDouble(TS.TotalHours);
                    break;
                case EnumDateCompare.minute:
                    diff = Convert.ToDouble(TS.TotalMinutes);
                    break;
                case EnumDateCompare.second:
                    diff = Convert.ToDouble(TS.TotalSeconds);
                    break;
            }
            return diff;
        }

        #endregion四.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;
}五.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六.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七.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);八获得当前日期是该年度的第几周
DateTime dt = Convert.ToDateTime("2006-05-01");
int weeks = dt.DayOfYear / 7 + 1;