using System;

​

public class Program

{

    public void Main()

    {

        Console.WriteLine(" Hello World! ".CenterString(80, '#'));

    }

}

​

public static class StringExtensions

{

    public static string CenterString(this string stringToCenter, int totalLength)

    {

        return stringToCenter.PadLeft(((totalLength - stringToCenter.Length) / 2) + stringToCenter.Length).PadRight(totalLength);

    }

​

    public static string CenterString(this string stringToCenter, int totalLength, char paddingCharacter)

    {

        return stringToCenter.PadLeft(((totalLength - stringToCenter.Length) / 2) + stringToCenter.Length, paddingCharacter).PadRight(totalLength, paddingCharacter);

    }

}