Question

I have a c# DateTime object and I need to increment it by one month.

example:

input           output ------------------------------- Jan 12, 2005    Feb 12, 2005 Feb 28, 2009    Mar 28, 2009 Dec 31, 2009    Jan 31, 2010 Jan 29, 2000    Feb 29, 2000 Jan 29, 2100    Error: no Feb 29, 2100 

What is the best way to do this.

My first thought (aside from some built in code) was to construct a new DateTime from pieces and handle the roll to the year myself

Answer 1

Here’s a complete program showing the examples given in the question. You’d probably want to use an exception in OneMonthAfter if it really shouldn’t be called that way.

using System; using System.Net;  public class Test {     static void Main(string[] args)     {         Check(new DateTime(2005, 1, 12));         Check(new DateTime(2009, 2, 28));         Check(new DateTime(2009, 12, 31));         Check(new DateTime(2000, 1, 29));         Check(new DateTime(2100, 1, 29));     }      static void Check(DateTime date)     {         DateTime? next = OneMonthAfter(date);         Console.WriteLine('{0} {1}', date,                           next == null ? (object) 'Error' : next);     }      static DateTime? OneMonthAfter(DateTime date)     {         DateTime ret = date.AddMonths(1);         if (ret.Day != date.Day)         {             // Or throw an exception             return null;         }         return ret;     } }