How to get the First and Last Day of the Current Week using a specific date in C#

using System;

namespace Tutorialsrack
{
    class Program
    {
        /*How to get First and Last day of the Current Week using specific date using C#*/
        static void Main(string[] args)
        {
            //initialize a datetime variable
            DateTime date = DateTime.Today;

            //Returns and Print First Day of Current Week
            Console.WriteLine("First Day of the Week is: {0}", datetimeext.GetFirstDayOfWeek(date).ToString("dd-MM-yyyy"));
            //Returns and Print Last Day of Current Week
            Console.WriteLine("Last Day of the Week is: {0}", datetimeext.GetLasttDayOfWeek(date).ToString("dd-MM-yyyy"));

            Console.ReadKey();
        }
    }

    static class datetimeext
    {
        //To Get The First Day of the Week in C#
        public static DateTime GetFirstDayOfWeek(this DateTime date)
        {
            var culture = System.Threading.Thread.CurrentThread.CurrentCulture;
            var diff = date.DayOfWeek - culture.DateTimeFormat.FirstDayOfWeek;
            if (diff < 0)
                diff += 7;
            return date.AddDays(-diff).Date;
        }

        //To Get The Last Day of the Week in C#
        public static DateTime GetLasttDayOfWeek(this DateTime date)
        {
            var culture = System.Threading.Thread.CurrentThread.CurrentCulture;
            var diff = date.DayOfWeek - culture.DateTimeFormat.FirstDayOfWeek;
            if (diff < 0)
                diff += 7;
            DateTime start = date.AddDays(-diff).Date;
            return start.AddDays(6).Date;
        }
    }
}

First Day of the Week is: 14-10-2019
Last Day of the Week is: 20-10-2019