.net c# 日期格式和常用处理

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);
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;