C#中时间的减法求出时间差

1.取某月的最后一天

 1    //1.使用算出该月多少天，年+月+加上多少天即可,举例取今天最后一天
 2         private static void GetLastDateForMonth(DateTime dtStart,out DateTime dtEnd)
 3         {
 4             int dtYear, dtMonth;
 5             //dtStart = DateTime.Now;
 6             dtYear = dtStart.Year;
 7             dtMonth = dtStart.Month;
 8             int MonthCount = DateTime.DaysInMonth(dtYear, dtMonth);
 9             dtEnd = Convert.ToDateTime(dtYear.ToString() + "-" + dtMonth.ToString() + "-" + MonthCount);
10 
11         }

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1       private static void GetLastDateForMonth(DateTime dtStart, out DateTime dtEnd)
2         {
3             int dtYear, dtMonth;
4             DateTime dtStart2= dtStart.AddMonths(1);
5             dtYear = dtStart2.Year;
6             dtMonth = dtStart2.Month;
7             dtEnd = Convert.ToDateTime(dtYear.ToString() + "-" + dtMonth.ToString() + "-" + "1").AddDays(-1);
8 
9         }

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2.时间差的计算TimeSpan

1  DateTime dt1 = new DateTime(2021, 5, 18, 14, 23,22);
2             DateTime dt2 = DateTime.Now;
3              TimeSpan ts = dt1.Subtract(dt2);
4             Console.WriteLine($"相差{ts.Days}天{ts.Hours}小时{ts.Minutes}分钟{ts.Seconds}秒");
5             Console.ReadKey(); 

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