using System;

public class Program

{

    public static void Main()

    {

        string[] ranges = new string[] { "today", "tomorrow", "thisweek", "thismonth", "nextweek", "nextmonth", "thisyear", "nextyear" };

        foreach (var r in ranges) {

            Console.WriteLine(r + " - " + CalculateFromTimeRange(r));   

        }

    }

    public static DateRange CalculateFromTimeRange(string range) 

    {

        DateTime startDate = DateTime.Now.Date;

        DateTime endDate = startDate.AddDays(1);

        switch (range) 

        {

            case "tomorrow":

                startDate = DateTime.Now.Date.AddDays(1);

                endDate = startDate.AddDays(1);

                break;

            case "thisweek":

                startDate = DateTime.Now.Date.AddDays(-1 * (int)DateTime.Now.DayOfWeek);

                endDate = startDate.AddDays(7);

                break;

            case "thismonth":

                startDate = DateTime.Parse(DateTime.Now.Month + "/1/" + DateTime.Now.Year);

                endDate = startDate.AddMonths(1);

                break;

            case "nextweek":

                startDate = DateTime.Now.Date.AddDays(7-(int)DateTime.Now.DayOfWeek);

                endDate = startDate.AddDays(7);

                break;

            case "nextmonth":

                startDate = DateTime.Parse(DateTime.Now.Month + "/1/" + DateTime.Now.Year).AddMonths(1);

                endDate = startDate.AddMonths(1);

                break;

            case "thisyear":

                startDate = DateTime.Parse("1/1/" + DateTime.Now.Year);

                endDate = startDate.AddYears(1);

                startDate = DateTime.Now.Date;

                break;

            case "nextyear":

                startDate = DateTime.Parse("1/1/" + (DateTime.Now.Year + 1));

                endDate = startDate.AddYears(1);

                break;      

            default: 

                // today is default case

                break;

        }

        return new DateRange () {

            StartDate = startDate,

            EndDate = endDate

        };

    }

    public class DateRange {

        public DateTime StartDate { get; set; }

        public DateTime EndDate { get; set; }

        public override string ToString() {

            return StartDate.ToShortDateString() + " - " + EndDate.ToShortDateString();

        }

    }

}