[B]Kleiner Programmierservice

public static class Converter
    {
        public static String convert(int fromBase, int toBase, String value)
        {
            String output = "";
            int[] valueA = new int[value.Length]; // zu dezimal
            valueA = getdigitUD(value);
            int decErgebnis = 0;
            for (int i = 0; i < value.Length; i++)
            {
                decErgebnis = decErgebnis + valueA[i] * Convert.ToInt32(Math.Pow(fromBase, i));
            }
            while (decErgebnis != 0) //das dezimale zur toBase
            {
                switch (decErgebnis % toBase)
                {
                    case 10:
                        output = "A" + output;
                        break;
                    case 11:
                        output = "B" + output;
                        break;
                    case 12:
                        output = "C" + output;
                        break;
                    case 13:
                        output = "D" + output;
                        break;
                    case 14:
                        output = "E" + output;
                        break;
                    case 15:
                        output = "F" + output;
                        break;
                    default:
                        output = (decErgebnis % toBase).ToString() + output;
                        break;
                }
                
                decErgebnis = decErgebnis / toBase;
            }
            return output;
        }
        private static int[] getdigitUD(String value)//digits verkehrtherum
        {
            String Svalue = value;
            int[] valueA = new int[value.Length];
            int i = 1;
            foreach (char ch in Svalue)
            {
                switch (ch.ToString())
                {
                    case "A":
                        valueA[value.Length - i] = 10;
                        break;
                    case "B":
                        valueA[value.Length - i] = 11;
                        break;
                    case "C":
                        valueA[value.Length - i] = 12;
                        break;
                    case "D":
                        valueA[value.Length - i] = 13;
                        break;
                    case "E":
                        valueA[value.Length - i] = 14;
                        break;
                    case "F":
                        valueA[value.Length - i] = 15;
                        break;
                    default:
                        valueA[value.Length - i] = Convert.ToInt32(ch.ToString());
                        break;
                }
                i++;
            }
            return valueA;

        }
    }