日期處理大全

1、 初始化

 DateTime dt = DateTime.Now;//1

DateTime dt = new DateTime();//2
DateTime dt = default(DateTime);//3

1,2,3都行

Date?  dt=null;不行

 

2  去掉日期中的時分秒

DateTime.ToShortDateString

 

 

3、將指定的天數加到此執行個體的值上。

DateTime.AddDays(double value);

 

4、每個月31天，每天增長1 

考慮到要和後面的日期比較，所以不能單獨購構造類寫個演算法，只好填充，每個月不到31天的填充一下

lines.Add(s);
                        int day = DateTime.DaysInMonth(curTime.Year, curTime.Month);
                        int curDay=curTime.Day;
                       
                        if (curDay==day&&curDay<31)
                        {
                            int nextDay = day + 1;
                            while (nextDay<= 31)
                            {
                               
                                string str = String.Format("{0,6}", curTime.Year) + String.Format("{0,5}", curTime.Month) + String.Format("{0,6}", nextDay);
                                string fillShu = "-99.9";
                                string sv = str + String.Format("{0,6}", fillShu) + String.Format("{0,6}", fillShu) + String.Format("{0,6}", fillShu);
                                lines.Add(sv);
                                nextDay++;
                            }
                           

                        }
                        curTime = curTime.AddDays(1);