Метод для работы с датой (вычисления трудоемкости разработки)

public class SoftwareProgram
    {
        private List<string> _opList = new List<string>();
        private DateTime date_start;
        private DateTime date_finish;
        private int countEmp;
 
 
 
        public SoftwareProgram(DateTime date_start, DateTime date_finish, int countEmp)
        {
 
            this.date_start = date_start;
            this.date_finish = date_finish;
            this.countEmp = countEmp;
 
 
        }
        public List<string> Operation
        {
            get
            { return _opList; }
        }
 
        public void AddOperation(string line)
        {
            Operation.Add(line);
        }
        public void CountOperations(List<string> list)
        {
            int k = 0;
 
            foreach (string i in list)
            {
                k = list.Count();
                Console.WriteLine(i);
                
 
            }
            Console.WriteLine("Count is ${0}", k);
 
 
        }
        public static void Main()
        {
            SoftwareProgram dtapi = new SoftwareProgram(new DateTime(2013, 1, 23), new DateTime(2014, 1, 23), 4);
 
            dtapi.AddOperation("Win");
            dtapi.AddOperation("Android");
            dtapi.AddOperation("MAC");
            dtapi.CountOperations(dtapi._opList);
 
 
 
 
        }
 
 
 
 
 
    }

public List<string> Operation
{
    get
    { return _opList; }
}

public void CountOperations(List<string> list)
{
    int k = 0;
 
    foreach (string i in list)
    {
        k = list.Count();
        Console.WriteLine(i);
    }
    Console.WriteLine("Count is ${0}", k);

public void CountOperations()
{
    foreach (string i in _opList)
    {
        Console.WriteLine(i);
    }
    Console.WriteLine("Count Operations is {0}", _opList.Count());
}

 public class SoftwareProgram
    {
        private List<string> _opList = new List<string>();
        private DateTime date_start;
        private DateTime date_finish;
        private int countEmp;
 
 
 
        public SoftwareProgram(DateTime date_start, DateTime date_finish, int countEmp)
        {
 
            this.date_start = date_start;
            this.date_finish = date_finish;
            this.countEmp = countEmp;
 
 
        }
       
 
        public void AddOperation(string line)
        {
            _opList.Add(line);
        }
        public void CountOperations()
        {
            
 
            foreach (string i in _opList)
            {
               
                Console.WriteLine(i);
                
 
            }
            Console.WriteLine("Count is ${0}", _opList.Count());
 
 
        }
 
        public void PersonMonth(DateTime date_start, DateTime date_finish,int countEMP)
        {
 
 
            DateTime startdate = date_start;
 
            DateTime endDate = date_finish;
            double timespan;
            int result = DateTime.Compare(startdate, endDate);
            if (result > 0)
            {
                throw new Exception(" is later than ");
            }
            else if (result == 0)
            {
                throw new Exception(" is the same time as ");
 
            }
            else
            {
 
                timespan = endDate.Subtract(startdate).Days / (365.25 / 12);
 
                Console.WriteLine("Date Difference (month): " + Math.Round(timespan, MidpointRounding.ToEven));
            }
            if (countEMP <= 0)
            {
                throw new FormatException("Number of emp is less or equals 0");
            }
            else
            {
                double td = timespan / countEMP;
                Console.WriteLine("Month/CountEmp: " + Math.Round(td, MidpointRounding.ToEven));
            }
 
 
        }
 
 
 
 
 
 
 
 
        public static void Main()
        {
            SoftwareProgram dtapi = new SoftwareProgram(new DateTime(2014, 2, 23), new DateTime(2013, 2, 23), 2);
 
            dtapi.AddOperation("Win");
            dtapi.AddOperation("Android");
            dtapi.AddOperation("MAC");
            dtapi.CountOperations();
            try
            {
                dtapi.PersonMonth(dtapi.date_start, dtapi.date_finish, dtapi.countEmp);
            }
            catch (FormatException exe)
            {
 
                Console.WriteLine("Error: " + exe.Message); ;
            }
            catch (Exception ex) {
                Console.WriteLine("Error: " + dtapi.date_start.ToString("yyyy/MM/dd") + ex.Message + dtapi.date_finish.ToString("yyyy/MM/dd")); 
            }
           
          
        }
 
    }

namespace SoftwareTest
{
    [TestClass]
    public class SoftwareTest
    {
        [TestMethod]
        [ExpectedException(typeof(Exception))]
        public void TestMethod1()
          
        {
            DateTime dateStart = new DateTime(2009, 8, 1);
            DateTime dateEnd = new DateTime(2008, 8, 1);
            int countEMP = 4;
            SoftwareProgram dtapi = new SoftwareProgram(dateStart,dateEnd,countEMP);
            dtapi.PersonMonth(dateStart, dateEnd, countEMP);
            
 
 
 
        }
    }
}

    public class SoftwareProgram
    {
        private List<string> opList = new List<string>();
        private IReadOnlyCollection<string> _opList;
        public IReadOnlyCollection<string> OpList => _opList ?? (_opList = opList.AsReadOnly());
        public DateTime DateStart { get; private set; }
        public DateTime DateFinish { get; private set; }
        public int CountEmp { get; private set; }
 
 
 
        public SoftwareProgram(DateTime dateStart, DateTime dateFinish, int countEmp)
        {
            DateStart = dateStart;
            DateFinish = dateFinish;
            CountEmp = countEmp;
        }
 
 
        public void AddOperation(string line) => opList.Add(line);
 
        public void ConsoleWriteOperations()
        {
            Console.WriteLine(string.Join(Environment.NewLine, OpList));
            Console.WriteLine($"Count is ${OpList.Count}");
        }
 
        public static void ConsoleWritePersonDays(DateTime dateStart, DateTime dateFinish, int countEMP)
        {
 
            TimeSpan interval = dateFinish - dateStart;
            double days = interval.TotalDays;
            if (days < 0)
                throw new Exception(" is later than ");
 
            if (days == 0)
                throw new Exception(" is the same time as ");
            if (countEMP <= 0)
                throw new FormatException("Number of emp is less or equals 0");
 
            Console.WriteLine($"Date Difference (days): {days:0}");
            Console.WriteLine($"Month/CountEmp: {days / countEMP:0}");
        }
        public void ConsoleWritePersonDays() => ConsoleWritePersonDays(DateStart, DateFinish, CountEmp);
 
        public static void ConsoleWritePersonMounts(DateTime dateStart, DateTime dateFinish, int countEMP)
        {
 
            TimeSpan interval = dateFinish - dateStart;
            double mounts = interval.TotalDays*12/365.25;
            if (mounts < 0)
                throw new Exception(" is later than ");
 
            if (mounts == 0)
                throw new Exception(" is the same time as ");
            if (countEMP <= 0)
                throw new FormatException("Number of emp is less or equals 0");
 
            Console.WriteLine($"Date Difference (mounts): {mounts:0}");
            Console.WriteLine($"Month/CountEmp: {mounts / countEMP:0}");
        }
        public void ConsoleWritePersonMounts() => ConsoleWritePersonMounts(DateStart, DateFinish, CountEmp);
 
    }