Data Types C#

using System;
using System.Globalization;
using System.Text;
using System.Numerics;
public class Class1
{
    public static void Main()
    {
        BigInteger number = BigInteger.Parse("~6", new BigIntegerFormatProvider());
        Console.WriteLine(number.ToString(new BigIntegerFormatProvider()));
        Console.WriteLine(number);
    }
}
public class BigIntegerFormatProvider : IFormatProvider
{
    public object GetFormat(Type formatType)
    {
        if (formatType == typeof(NumberFormatInfo))
        {
            NumberFormatInfo numberFormat = new NumberFormatInfo();
            numberFormat.NegativeSign = "~";
            return numberFormat;
        }
        else
        {
            return null;
        }
    }
}