C# get first day of month
- C# get first day of month from date
- C# get first day of next month
- C# get first day of previous month
- C# get first business day of month
- C# datetime get first day of next month
- C# first day of month from date
- C# datetime get first and last day of month
- C# get first and last day of current month
- C# datetimeoffset first day of month
- C# get first and last day of month from date
- C# get first and last day of previous month