// C# Extension Method

// Doc: https://csharp-extension.com/en/method/1002399/int32-daysinmonth

​

// @nuget: Z.ExtensionMethods

​

using System;

using System.Globalization;

public class Program

{

    public static void Main()

    {

        int[] years = { 2016, 2019 };

        DateTimeFormatInfo dtfi = DateTimeFormatInfo.CurrentInfo;

        Console.WriteLine("Days in the Month for the {0} culture using the {1} calendar\n", CultureInfo.CurrentCulture.Name, dtfi.Calendar.GetType().Name.Replace("Calendar", ""));

        Console.WriteLine("{0,-10}{1,-15}{2, -4}\n", "Year", "Month", "Days");

​

        foreach (var year in years)

        {

            for (int ctr = 0; ctr <= dtfi.MonthNames.Length - 1; ctr++)

            {

                if (String.IsNullOrEmpty(dtfi.MonthNames[ctr]))

                    continue;

​

                // C# Extension Method: Int32 - DaysInMonth

                Console.WriteLine("{0,-10}{1,-15}{2, -4}", year, dtfi.MonthNames[ctr], year.DaysInMonth(ctr + 1));

            }

            Console.WriteLine();

        }

    }

}