C#计算时间--按照日期确定第几周 按照第几周确定日期范围

using System;
using System.Globalization;
namespace ConvertDateTime
{
/// <summary>
/// ConvertDateTime の概要の説明です。

/// </summary>
public class ConvertDate
{
   public ConvertDate()
   {}
   //*******************************************************************//
   #region 根据当前日期确定当前是星期几  
   public static string GetWeekDay(string strDate)
   {
    try
    {
     //需要判断的时间
     DateTime dTime = Convert.ToDateTime(strDate);

     return GetWeekDay(dTime);
    }
    catch(Exception ex)
    {
     throw new Exception(ex.Message);
    }
   
   }
   public static string GetWeekDay(DateTime dTime)
   {
    try
    {
     //确定星期几
     int index = (int)dTime.DayOfWeek;
     return GetWeekDay(index);
    }
    catch(Exception ex)
    {
     throw new Exception(ex.Message);
    }
   
   }
   #endregion

   //*******************************************************************//
   #region 获取当前年的最大周数  
   public static int GetMaxWeekOfYear(int year)
   {
    try
    {
     DateTime tempDate = new DateTime(year,12,31);
     int tempDayOfWeek = (int)tempDate.DayOfWeek;
     if(tempDayOfWeek != 0)
     {
      tempDate = tempDate.Date.AddDays(-tempDayOfWeek);
     }
     return GetWeekIndex(tempDate);
    }
    catch(Exception ex)
    {
     throw new Exception(ex.Message);
    }
   }
   public static int GetMaxWeekOfYear(DateTime dTime)
   {
    try
    {
     return GetMaxWeekOfYear(dTime.Year);
    }
    catch(Exception ex)
    {
     throw new Exception(ex.Message);
    }
   }
   #endregion

   //*******************************************************************//
   #region 根据时间获取当前是第几周

   //如果12月31号与下一年的1月1好在同一个星期则算下一年的第一周
   public static int GetWeekIndex(DateTime dTime)
   {
    try
    {
     //需要判断的时间
     //DateTime dTime = Convert.ToDateTime(strDate);
     //确定此时间在一年中的位置
     int dayOfYear = dTime.DayOfYear;

     //DateTime tempDate = new DateTime(dTime.Year,1,6,calendar);
     //当年第一天
     DateTime tempDate = new DateTime(dTime.Year,1,1);

     //确定当年第一天
     int tempDayOfWeek = (int)tempDate.DayOfWeek;
     tempDayOfWeek = tempDayOfWeek==0?7:tempDayOfWeek;
     //确定星期几
     int index = (int)dTime.DayOfWeek;

     index = index==0?7:index;

     //当前周的范围
     DateTime retStartDay = dTime.AddDays(-(index-1));
     DateTime retEndDay = dTime.AddDays(7-index);

     //确定当前是第几周
     int weekIndex = (int)Math.Ceiling(((double)dayOfYear+tempDayOfWeek-1)/7);
               

     if(retStartDay.Year < retEndDay.Year)
     {
      weekIndex = 1;
     }

     return weekIndex;
    }
    catch(Exception ex)
    {
     throw new Exception(ex.Message);
    }
    //string retVal = retStartDay.ToString("yyyy/MM/dd") + "～" + retEndDay.ToString("yyyy/MM/dd");
   
   }
   public static int GetWeekIndex(string strDate)
   {
    try
    {
     //需要判断的时间
     DateTime dTime = Convert.ToDateTime(strDate);
     return GetWeekIndex(dTime);
    }
    catch(Exception ex)
    {
     throw new Exception(ex.Message);
    }

   }
   #endregion

   //*******************************************************************//
   #region 根据时间取周的日期范围

   public static string GetWeekRange(string strDate)
   {
    try
    {
     //需要判断的时间
     DateTime dTime = Convert.ToDateTime(strDate);
     return GetWeekRange(dTime);
    }
    catch(Exception ex)
    {
     throw new Exception(ex.Message);
    }
   }
   public static string GetWeekRange(DateTime dTime)
   {
    try
    {
     int index = (int)dTime.DayOfWeek;

     index = index==0?7:index;

     //当前周的范围
     DateTime retStartDay = dTime.AddDays(-(index-1));
     DateTime retEndDay = dTime.AddDays(7-index);

     return WeekRangeToString(retStartDay,retEndDay);
    }
    catch(Exception ex)
    {
     throw new Exception(ex.Message);
    }

   }

   public static string GetWeekRange(int year,int weekIndex)
   {
    try
    {
     if(weekIndex < 1)
     {
      throw new Exception("请输入大于0的整数");
     }
    
     int allDays = (weekIndex-1)*7;
     //确定当年第一天
     DateTime firstDate = new DateTime(year,1,1);
     int firstDayOfWeek = (int)firstDate.DayOfWeek;

     firstDayOfWeek = firstDayOfWeek==0?7:firstDayOfWeek;

     //周开始日
     int startAddDays = allDays + (1 - firstDayOfWeek);
     DateTime weekRangeStart = firstDate.AddDays(startAddDays);
     //周结束日
     int endAddDays = allDays + (7 - firstDayOfWeek);
     DateTime weekRangeEnd = firstDate.AddDays(endAddDays);

     if(weekRangeStart.Year > year ||
      (weekRangeStart.Year == year && weekRangeEnd.Year > year))
     {
      throw new Exception("今年没有第"+weekIndex+"周。");
     }

     return WeekRangeToString(weekRangeStart,weekRangeEnd);
    }
    catch(Exception ex)
    {
     throw new Exception(ex.Message);
    }
   }
   public static string GetWeekRange(int weekIndex)
   {
    try
    {    
     return GetWeekRange(DateTime.Now.Year,weekIndex);
    }
    catch(Exception ex)
    {
     throw new Exception(ex.Message);
    }
   }

   private static string WeekRangeToString(DateTime weekRangeStart,DateTime weekRangeEnd)
   {
    string strWeekRangeStart = weekRangeStart.ToString("yyyy/MM/dd");
    string strWeekRangeend = weekRangeEnd.AddDays.ToString("yyyy/MM/dd");

    return strWeekRangeStart + "～" + strWeekRangeend;

   }
   #endregion

   //*******************************************************************//
   #region 转换星期的表示方法

   private static string GetWeekDay(int index)
   {
    string retVal = string.Empty;
    switch(index)
    {
     case 0:
     {
      retVal = "星期日";
      break;
     }
     case 1:
     {
      retVal = "星期一";
      break;
     }
     case 2:
     {
      retVal = "星期二";
      break;
     }
     case 3:
     {
      retVal = "星期三";
      break;
     }
     case 4:
     {
      retVal = "星期四";
      break;
     }
     case 5:
     {
      retVal = "星期五";
      break;
     }
     case 6:
     {
      retVal = "星期六";
      break;
     }
    }

    return retVal;
   }
   #endregion
}
}