tester2

using System;
/* a helper class, Tester, begun in Lesson 5 and now extended in
Lesson 6 of intro C# console programming series found at the
following URL:
http://williammillerservices.com/windows-c-console-programming/

GitHub gist -> https://gist.github.com/kyrathasoft/1a2b341e6ae8e97c91c68e51082c1409
Pastebin.com -> https://pastebin.com/nKVkikZ8

note: to use, you would reference the file containing this code
from your primary program file. If you have the following program...

using System;
using TestInput;

namespace MyNS{
    class MyCls{
        public static void Main(){
            string sNum = "4";
            if(Tester.IsInteger(sNum)){
                Console.WriteLine("Yes, we can parse {0} to an int.", sNum);
            }
        }
    }
}

...and if above program named test.cs and below is tester.cs and in
same directory, then we'd compile like so:

csc /out:test.exe test.cs tester.cs

Running resulting test.exe would produce: Yes, we can parse 4 to an int.

Or, we could make tester.cs code into DLL via:
csc /t:library tester.cs

...and then compile like so:
csc /r:tester.dll test.cs

*/


namespace TestInput
{
    public class Tester
    {
        public static bool IsInteger(string p)
        {
            bool result = false;
            int i;

            if (int.TryParse(p, out i))
            {
                result = true;
            }

            return result;
        }

    }

    public static int GetDifferenceInYears(DateTime startDate, DateTime endDate)
{
        //Excel documentation says "COMPLETE calendar years in between dates"
        int years = endDate.Year - startDate.Year;

        if (startDate.Month == endDate.Month &&// if the start month and the end month are the same
            endDate.Day < startDate.Day// AND the end day is less than the start day
            || endDate.Month < startDate.Month)// OR if the end month is less than the start month
        {
            years--;
        }

        return years;
}

}