C#中怎样将小数转变成分数形式

                string result = default(string);
                Console.WriteLine("Input:");
                string input = Console.ReadLine();
                try
                {
                   double inputnum = Convert.ToDouble(input);
                   string[] array = inputnum.ToString().Split('.');
                   int len = array[1].Length;
                   int num = Convert.ToInt32(Math.Pow(10, len));
                   int value = Convert.ToInt32(inputnum * num);
                   int a = value;
                   int b = num;
                   while (a != b)
                   {
                       if (a > b)
                           a = a - b;
                       else
                           b = b - a;
                   }
                   value = value / a;
                   num = num / a;
                   result = string.Format("{0}/{1}", value, num);
                }
                catch (Exception)
                {
                    result = input.ToString();
                }
                
                Console.WriteLine("Result:{0}", result);
                Console.ReadLine();