C# - Größter gemeinsamer Teiler

public static int GetGreatestCommenDivisor(IEnumerable<int> source)
        {
            Dictionary<int, int> primes = new Dictionary<int, int>();
            bool firstRun = true;
            foreach (int i in source)
            {
                if (firstRun)
                {
                    firstRun = false;
                    primes = PrimeFactorization(i);
                }
                else
                {
                    Dictionary<int, int> temp = PrimeFactorization(i);
                    foreach (var item in temp)
                    {
                        if (primes.ContainsKey(item.Key))
                        {
                            if (primes[item.Key] > item.Value)
                            {
                                primes[item.Key] = item.Value;
                            }
                        }

                        for (int j = 0; j != primes.Count; j++)
                        {
                            int key = primes.Keys.ElementAt(j);
                            if (!temp.ContainsKey(key))
                            {
                                primes[key] = 0;
                            }
                        }
                    }
                }
            }

            int maxDivisor = 1;
            foreach (var item in primes)
            {
                maxDivisor *= Convert.ToInt32(Math.Pow(item.Key, item.Value));
            }
            return maxDivisor;
        }

public static Dictionary<int, int> PrimeFactorization(int a)
        {
            Dictionary<int, int> primes = new Dictionary<int, int>();
            for (int b = 2; a > 1; b++)
                if (a % b == 0)
                {
                    int x = 0;
                    while (a % b == 0)
                    {
                        a /= b;
                        x++;
                    }
                    primes.Add(b, x);
                }
            return primes;
        }