How to calculate factorial with single line of code in C#

using System;
using System.Linq;
using System.Numerics;

public static class Factorial
{
    public static void Main(string[] args)
    {
        int num = 100;
        Console.WriteLine(Enumerable.Range(1, num).Select(i => new BigInteger(i)).Aggregate((a, b) => a * b));
    }
}
// 93326215443944152681699238856266700490715968264381621468592963895217599993229915608941463976156518286253697920827223758251185210916864000000000000000000000000

How to convert decimal number to hexadecimal in C# using method

    using System;
    using System.Text;

    class DecToHex
    {
        static void Main(string[] args)
        {
            long num = 100000;
            Console.WriteLine(DecimalToHex(num)); // 186A0
        }

        private static string DecimalToHex(long num)
        {
            var res = new StringBuilder();
            while (num > 0)
            {
                var reminder = num % 16;
                if (reminder > 9)
                {
                    res.Insert(0, (char)(reminder + 55));
                }
                else
                {
                    res.Insert(0, reminder);
                }

                num /= 16;
            }

            return res.ToString();
        }
    }

How to convert decimal to binary number in C# using method

    using System;
    using System.Text;

    class DecToBin
    {
        static void Main(string[] args)
        {
            long num = int.MaxValue * 2L;
            Console.WriteLine(DecimalToBinary(num)); // 11111111111111111111111111111110
        }

        private static string DecimalToBinary(long num)
        {
            StringBuilder res = new StringBuilder();
            while (num > 0)
            {
                res.Insert(0, num % 2);
                num /= 2;
            }

            return res.ToString();
        }
    }

How to convert binary number to decimal in C# using method.

using System;

    class BinToDec
    {
        static void Main(string[] args)
        {
            string binary = "101";
            Console.WriteLine(BinaryToDecimal(binary)); // will return 5

        }

        private static long BinaryToDecimal(string binary)
        {
            long decimalNum = 0;
            for (int i = binary.Length - 1, pow = 0; i >= 0; i--, pow++)
            {
                decimalNum += int.Parse(binary[i].ToString()) * (long)Math.Pow(2, pow);
            }

            return decimalNum;
        }
    }

Replace multiply whitespaces with single space inside text using C#.

using System;
using System.Text.RegularExpressions;

static class ReplaceWhiteSpaces
{
    public static void Main()
    {
        string text = "This is some   text    with        whitespaces in    it   . :     )";
        Console.WriteLine(Regex.Replace(text, @"(\s)\1+", " "));
    }
}

Easy way to find all palindromes inside string array using C#.

using System;
using System.Linq;

static class Palindromes
{
    private static void Main()
    {
        string[] words = { "test", "notPalindrome", "azuruza", "aha", "what?", "b" };
        Console.WriteLine(string.Join(", ", words.Where(w => w.SequenceEqual(w.Reverse()))));
    }
}