C# Numeric Base Conversion

Base.cs

// Copyright (c) 2015 David Ruhmann

using System;
using System.Collections.Generic;
using System.Text;

namespace ChartedCode
{
    public static class NumberExtensions
    {
        public static string ToBase(this int value, int radix, string digits)
        {
            if (string.IsNullOrEmpty(digits))
            {
                throw new ArgumentNullException("digits", string.Format("Digits must contain character value representations"));
            }

            radix = Math.Abs(radix);
            if (radix > digits.Length || radix < 2)
            {
                throw new ArgumentOutOfRangeException("radix", radix, string.Format("Radix has to be > 2 and < {0}", digits.Length));
            }

            string result = string.Empty;
            int quotient = Math.Abs(value);
            while (0 < quotient)
            {
                int temp = quotient % radix;
                result = digits[temp] + result;
                quotient /= radix;
            }
            return result;
        }
    }
    
    public static class StringExtensions
    {
        public static int FromBase(this string text, int radix, string digits, bool forgive = false)
        {
            if (string.IsNullOrEmpty(digits))
            {
                throw new ArgumentNullException("digits", string.Format("Digits must contain character value representations"));
            }

            radix = Math.Abs(radix);
            if (radix > digits.Length || radix < 2)
            {
                throw new ArgumentOutOfRangeException("radix", radix, string.Format("Radix has to be > 2 and < {0}", digits.Length));
            }

            // Convert to Base 10
            int value = 0;
            if (!string.IsNullOrEmpty(text))
            {
                for (int i = text.Length - 1; i >= 0; --i)
                {
                    int temp = digits.IndexOf(text[i]) * (int)Math.Pow(radix, text.Length - (i + 1));
                    if (0 > temp && !forgive)
                    {
                        throw new IndexOutOfRangeException("Text contains characters not found in digits.");
                    }
                    value += temp;
                }
            }
            return value;
        }

        public static string ToBase(this string text, int fromRadix, string fromDigits, int toRadix, string toDigits)
        {
            return text.FromBase(fromRadix, fromDigits).ToBase(toRadix, toDigits);
        }

        public static string ToBase(this string text, int from, int to, string digits)
        {
            return text.FromBase(from, digits).ToBase(to, digits);
        }
    }
}