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public static class LocationExtensions
{
    private const double RadianHalfPiToDegrees = 90.0;
    private const double RadianPiToDegrees = 180.0;
    private const double RadianTwoPiToDegrees = 360.0;
    private static readonly Location _center = new Location(latitude: 0, longitude: 0);
    private static readonly Location _northeast = new Location(latitude: RadianHalfPiToDegrees, longitude: RadianPiToDegrees);
    private static readonly Location _southwest = new Location(latitude: -RadianHalfPiToDegrees, longitude: -RadianPiToDegrees);

    private static Location GetValidLocation(double latitude, double longitude)

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public class JoinPointExample
{
    private const int Max = 10000000;

    private static int SumDigits(int num)
    {
        int sum = 0;

        while (num > 0)
        {

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public static class ArrayExtensions
{
    public static void MergeSort(this int[] array, int left, int right)
    {
        if (left >= right)
            return;
        var mid = (left + right) / 2;
        MergeSort(array, left, mid);
        MergeSort(array, mid + 1, right);
        DoMerge(array, left, mid, right);

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using System.Runtime.CompilerServices;

/// <summary>
/// EagerLoad<T> provides support for asynchronous cached eager initialization. This type is fully threadsafe.
/// Lazy<T> is for caching a value and synchronizing multiple threads attempting to get at that cached value.
/// Task<T> is for representing an asynchronous operation and making its result available in the future.
/// <see href="https://devblogs.microsoft.com/pfxteam/asynclazyt/"/>
/// <seealso href="https://blog.stephencleary.com/2012/08/asynchronous-lazy-initialization.html"/>
/// <seealso href="https://github.com/StephenCleary/AsyncEx/blob/master/src/Nito.AsyncEx.Coordination/AsyncLazy.cs"/>
/// </summary>

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public class SslCertificateHelper
{
    [SupportedOSPlatform("windows")]
    public static X509Certificate2? GetX509Certificate2(string subject = "CN=localhost")
    {
        X509Certificate2? certificate = null;
        using var certStore = new X509Store(StoreName.My, StoreLocation.LocalMachine);
        certStore.Open(OpenFlags.ReadWrite | OpenFlags.OpenExistingOnly);
        var certs = certStore.Certificates.Find(X509FindType.FindBySubjectDistinguishedName, subject, false);
        if (certs.Count > 0)

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private static string ReadPasswordFromConsole()
{
        Console.TreatControlCAsInput = true;
	var sb = new StringBuilder();
	while (Console.ReadKey(true) is ConsoleKeyInfo cki && cki.Key != ConsoleKey.Enter)
	{
                if (cki.Modifiers == ConsoleModifiers.Control && cki.Key == ConsoleKey.C)
	        {
			break;
		}

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public class StringExtensions
{
    internal static string ReplaceFirstInstanceOf(this string? original, string oldValue, string newValue)
    {
        string result = string.Empty;
        if (!string.IsNullOrEmpty(original))
        {
            int index = original.IndexOf(oldValue);
            result = index < 0 ? original : index == 0 ? string.Concat(newValue, original.AsSpan(oldValue.Length)) :
                string.Concat(original.AsSpan(0, index), newValue, original.AsSpan(index + oldValue.Length));

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public class DigitsOnly
{
      public static string Get(string text)
      {
          string result = string.Empty;
          if (!string.IsNullOrWhiteSpace(text))
          {
              var sb = new StringBuilder(text.Length);
              for (int i = 0; i < text.Length; i++)
                  if (text[i] >= '0' && text[i] <= '9')

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public class Luhn
{
    public static bool CheckLuhnDigit(string digits, int last = 1)
    {
        var checksum = CalculateLuhnDigit(digits, last);
        int checkDigit = checksum > -1 ? digits[^last] - '0' : 0;
        return checksum == checkDigit;
    }

    public static int CalculateLuhnDigit(string digits, int lastIndex = 0)