How to find the first day of next month,if the current month is december

Question

I\'m using the following query to get the next month.

int theMonth = ((System.DateTime)periodStartDate).Month+1;

But if the periodstartDate

Answer 1

DateTime date = DateTime.Now;
Console.WriteLine(date);
// Sunday 28.06.2015 г. 10:22:41 ч.

int monthsBack = -1;
int whichDay = 1;
// It means -> what day the first day of the previous month is.
DayOfWeek FirstDayOfWeek = date.AddMonths(monthsBack).AddDays(whichDay).DayOfWeek;
Console.WriteLine(FirstDayOfWeek);
// Friday

int delta = DayOfWeek.Monday - date.AddMonths(monthsBack).AddDays(whichDay).DayOfWeek;
Console.WriteLine(delta);
// -4
//-4 ->Monday , -3 ->Tuesday, -2 ->Wednesday , -1 ->Thursday, 0 ->Friday