在C#的开发当中经常遇到关于一个日期时间"+/-"一段时间的问题,下面是一些相关总结,供大家参考.
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
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/// /// 计算本周起始日期(礼拜一的日期)
///
/// 该周中任意一天
/// 返回礼拜一日期，后面的具体时、分、秒和传入值相等
public static DateTime CalculateFirstDateOfWeek(DateTime someDate)
{
int i = someDate.DayOfWeek - DayOfWeek.Monday;
if (i == -1) i = 6;// i值 > = 0 ，因为枚举原因，Sunday排在最前，此时Sunday-Monday=-1，必须+7=6。
TimeSpan ts = new TimeSpan(i, 0, 0, 0);
return someDate.Subtract(ts);
}
/// /// 计算本周结束日期(礼拜日的日期)
///
/// 该周中任意一天
/// 返回礼拜日日期，后面的具体时、分、秒和传入值相等
public static DateTime CalculateLastDateOfWeek(DateTime someDate)
{
int i = someDate.DayOfWeek - DayOfWeek.Sunday;
if(i != 0) i = 7 - i;// 因为枚举原因，Sunday排在最前，相减间隔要被7减。
TimeSpan ts = new TimeSpan(i, 0, 0, 0);
return someDate.Add(ts);
}
/// /// 判断选择的日期是否是本周(根据系统当前时间决定的‘本周’比较而言)
///
///
///
public static bool IsThisWeek(DateTime someDate)
{
//得到someDate对应的周一
DateTime someMon = CalculateFirstDateOfWeek(someDate);
//得到本周一
DateTime nowMon = CalculateFirstDateOfWeek(DateTime.Now);
TimeSpan ts = someMon - nowMon;
if (ts.Days < 0)
ts = -ts;//取正
if (ts.Days >= 7)
{
return false;
}
else
{
return true;
}
}
