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  • 所在周的第一天

    using System;  
    using System.Collections.Generic;  
    using System.Linq;  
    using System.Text;  
      
    namespace WyfClass  
    {  
    public class tools  
    {  
    /// <summary>  
    /// 得到本周第一天(以星期天为第一天)  
    /// </summary>  
    /// <param name="datetime"></param>  
    /// <returns></returns>  
    public DateTime GetWeekFirstDaySun(DateTime datetime)  
    {  
        //星期天为第一天  
        int weeknow = Convert.ToInt32(datetime.DayOfWeek);  
        int daydiff = (-1) * weeknow;  
      
        //本周第一天  
        string FirstDay = datetime.AddDays(daydiff).ToString("yyyy-MM-dd");  
        return Convert.ToDateTime(FirstDay);  
    }  
      
    /// <summary>  
    /// 得到本周第一天(以星期一为第一天)  
    /// </summary>  
    /// <param name="datetime"></param>  
    /// <returns></returns>  
    public DateTime GetWeekFirstDayMon(DateTime datetime)  
    {  
        //星期一为第一天  
        int weeknow = Convert.ToInt32(datetime.DayOfWeek);  
      
        //因为是以星期一为第一天,所以要判断weeknow等于0时,要向前推6天。  
        weeknow = (weeknow == 0 ? (7 - 1) : (weeknow - 1));  
        int daydiff = (-1) * weeknow;  
      
        //本周第一天  
        string FirstDay = datetime.AddDays(daydiff).ToString("yyyy-MM-dd");  
        return Convert.ToDateTime(FirstDay);  
    }  
      
    /// <summary>  
    /// 得到本周最后一天(以星期六为最后一天)  
    /// </summary>  
    /// <param name="datetime"></param>  
    /// <returns></returns>  
    public DateTime GetWeekLastDaySat(DateTime datetime)  
    {  
        //星期六为最后一天  
        int weeknow = Convert.ToInt32(datetime.DayOfWeek);  
        int daydiff = (7 - weeknow) - 1;  
      
        //本周最后一天  
        string LastDay = datetime.AddDays(daydiff).ToString("yyyy-MM-dd");  
        return Convert.ToDateTime(LastDay);  
    }  
      
    /// <summary>  
    /// 得到本周最后一天(以星期天为最后一天)  
    /// </summary>  
    /// <param name="datetime"></param>  
    /// <returns></returns>  
    public DateTime GetWeekLastDaySun(DateTime datetime)  
    {  
        //星期天为最后一天  
        int weeknow = Convert.ToInt32(datetime.DayOfWeek);  
        weeknow = (weeknow == 0 ? 7 : weeknow);  
        int daydiff = (7 - weeknow);  
      
        //本周最后一天  
        string LastDay = datetime.AddDays(daydiff).ToString("yyyy-MM-dd");  
        return Convert.ToDateTime(LastDay);  
    }  
    }  
    }  
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  • 原文地址:https://www.cnblogs.com/xuguanghui/p/7771986.html
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