C # time Comparison size

1. Time Comparison size

datetime t1 = new datetime (100);
DateTime t2 = new DateTime (20);

if (Datetime.compare (t1, T2) > 0) Console.WriteLine ("T1 > t2"); T1 Big
if (Datetime.compare (t1, t2) = = 0) Console.WriteLine ("T1 = = t2"); Equal
if (Datetime.compare (t1, T2) < 0) Console.WriteLine ("T1 < T2"); T1 Small

2. Get last day and first day of last month

Get last month
DateTime Lastmonth = DateTime.Now.AddMonths (-1);
Get the first day of last month
String lastmonth_firstday = Lastmonth.adddays (1-lastmonth.day). ToString ("Yyyy-mm-dd");
Get last day of last month
String lastmonth_lastday = Lastmonth.adddays (1-lastmonth.day). AddMonths (1). AddDays (-1). ToString ("Yyyy-mm-dd");

C # time Comparison size