• c#DateTime相关运用合集


    ① 获取当月开始日期和结束日期

    DateTime currentTime = DateTime.Now;
    DateTime CurrentMonthStart = DateTime.Parse($"{currentTime.Year}-{currentTime.Month+1}-1");//当月开始日期
    int days=System.Threading.Thread.CurrentThread.CurrentUICulture.Calendar.GetDaysInMonth(currentTime.Year, currentTime.Month+1);//当月天数
    
    DateTime CurrentMonthEnd = DateTime.Parse($"{currentTime.Year}-{currentTime.Month+1}-{days}");//当月结束日期

    ②获取本周开始时间和结束时间

    DateTime weekstar = DateTime.Parse(DateTime.Now.AddDays(-(int)DateTime.Now.DayOfWeek + 1).ToString("yyyy-MM-dd 00:00:00"));
    DateTime weekend = DateTime.Parse(DateTime.Now.AddDays(7 -(int)DateTime.Now.DayOfWeek).ToString("yyyy-MM-dd 23:59:59"));

    ③ 获取当月第一天和下个月第一天

    DateTime DateNow = DateTime.Now;
    DateTime DateBegin1 = new DateTime(DateNow.Year, DateNow.Month, 1);//当月第一天
    //获取下个月第一天
    DateTime DateNow1 = DateNow.AddMonths(1);
    DateTime DateBegin2 = new DateTime(DateNow1.Year, DateNow1.Month, 1);//下个月第一天

    ④ 计算两个日期之间相差的天数

    相关参考网址:https://blog.csdn.net/zht666/article/details/21601403

                          https://blog.csdn.net/e_wsq/article/details/7278760

    TimeSpan ts1 = new TimeSpan(time1.Ticks);
    TimeSpan ts2 = new TimeSpan(time2.Ticks);
    TimeSpan ts = time1.Subtract(time2.Now).Duration();
    int dateDiff = ts.Days;

    ⑤今天是星期几

    1.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" };
    string week = Day[Convert.ToInt32(DateTime.Now.DayOfWeek.ToString("d"))].ToString();
    lbDay.Text = week; 
    2.
    public static string dt;
    public static string week;
    dt = DateTime.Today.DayOfWeek.ToString();
    switch (dt)
    {
    case "Monday":
    week = "星期一";
    break;
    case "Tuesday":
    week = "星期二";
    break;
    case "Wednesday":
    week = "星期三";
    break;
    case "Thursday":
    week = "星期四";
    break;
    case "Friday":
    week = "星期五";
    break;
    case "Saturday":
    week = "星期六";
    break;
    case "Sunday":
    week = "星期日";
    break;
    }
    lbDay.Text = week; 
    3.string Week =System.Globalization.CultureInfo.CurrentCulture.DateTimeFormat.GetDayName(DateTime.Now.DayOfWeek);

    ⑥查询某月某周几的日期

      foreach (MaintenanceDutyPsersonDto item in maintenanceDuty)
                    {
                        string yearandmonth = item.DutyDate.ToString("yyyy-MM");
                        int year = item.DutyDate.Year;
                        int month = item.DutyDate.Month;
                        int d = DateTime.DaysInMonth(year, month);   //获取指定年月的天数
                        if (item.Dutymodel == "")//按周排班
                        {
                            string[] weeks = item.weeks;
                            List<string> datelist1 = new List<string>();
                            for (int i = 0; i < weeks.Length; i++)
                            {
                                switch (weeks[i])
                                {
                                    case "周一":
                                        for (int a = 1; a <= d; a++)
                                        {
                                            DateTime dt = new DateTime(year, month, a);
                                            if (dt.DayOfWeek == DayOfWeek.Monday)
                                            {
                                             
                                              datelist1.Add(dt.ToShortDateString());
                                              
                                            }
                                        }
                                        break;
                                    case "周二":
                                        for (int a = 1; a <= d; a++)
                                        {
                                            DateTime dt = new DateTime(year, month, a);
                                            if (dt.DayOfWeek == DayOfWeek.Tuesday)
                                            {
    
                                                datelist1.Add(dt.ToShortDateString());
    
                                            }
                                        }
                                        break;
                                    case "周三":
                                        for (int a = 1; a <= d; a++)
                                        {
                                            DateTime dt = new DateTime(year, month, a);
                                            if (dt.DayOfWeek == DayOfWeek.Wednesday)
                                            {
    
                                                datelist1.Add(dt.ToShortDateString());
    
                                            }
                                        }
                                        break;
                                    case "周四":
                                        for (int a = 1; a <= d; a++)
                                        {
                                            DateTime dt = new DateTime(year, month, a);
                                            if (dt.DayOfWeek == DayOfWeek.Thursday)
                                            {
    
                                                datelist1.Add(dt.ToShortDateString());
    
                                            }
                                        }
                                        break;
                                    case "周五":
                                        for (int a = 1; a <= d; a++)
                                        {
                                            DateTime dt = new DateTime(year, month, a);
                                            if (dt.DayOfWeek == DayOfWeek.Friday)
                                            {
    
                                                datelist1.Add(dt.ToShortDateString());
    
                                            }
                                        }
                                        break;
                                    case "周六":
                                        for (int a = 1; a <= d; a++)
                                        {
                                            DateTime dt = new DateTime(year, month, a);
                                            if (dt.DayOfWeek == DayOfWeek.Saturday)
                                            {
    
                                                datelist1.Add(dt.ToShortDateString());
    
                                            }
                                        }
                                        break;
                                    case "周日":
                                        for (int a = 1; a <= d; a++)
                                        {
                                            DateTime dt = new DateTime(year, month, a);
                                            if (dt.DayOfWeek == DayOfWeek.Sunday)
                                            {
    
                                                datelist1.Add(dt.ToShortDateString());
    
                                            }
                                        }
                                        break;
                                    default:
    
                                        break;
    
                                }
                            }

    ⑦ 获取某段日期范围内的所有日期

    /// <summary>
    /// 获取某段日期范围内的所有日期,以数组形式返回 
    /// </summary> 
    /// <param name="dt1">开始日期</param> 
    /// <param name="dt2">结束日期</param> 
    /// <returns></returns> 
    private DateTime[] GetAllDays(DateTime dt1, DateTime dt2)
    {
        List<DateTime> listDays = new List<DateTime>();
        DateTime dtDay = new DateTime();
        for (dtDay = dt1; dtDay.CompareTo(dt2) <= 0; dtDay = dtDay.AddDays(1))
        {
            listDays.Add(dtDay);
        }
        return listDays.ToArray();
    }

    ⑧判断某个日期是否在某段日期范围内

    /// <summary>
    /// 获取某段日期范围内的所有日期,以字符串形式返回
    /// </summary>
    /// <param name="startDate">开始日期</param>
    /// <param name="endDate">结束日期</param>
    /// <returns></returns>
    protected string GetDate(DateTime startDate, DateTime endDate)
    {
        string result = string.Empty;
        for (DateTime temp = startDate.ToShortDateString(); temp <= endDate.ToShortDateString(); temp = temp.AddDays(1))
        {
            if (result == string.Empty)
            {
                result = temp.ToString();
            }
            else
            {
                result += "," + temp.ToString();
            }
        }
        return result;
    }

    ⑨  C#时间类型 DateTime? 赋空值 关于datetime类型的DBNull判断

    public DateTime? SubTime { get; set; }
      //日期类型判断是否为null 用nullable这个泛型结构体
      m.SubTime=dr["subtime"]==DBNull.Value?new Nullable<DateTime>():Convert.ToDateTime(dr["subtime"])

    ⑩合集

    /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(); 
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  • 原文地址:https://www.cnblogs.com/cyqdeshenluo/p/12166654.html
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