csharp creating a hash table linked list

                
                        class Program
        {

        public class MyHashTable
        {
            public Node[] universe;
            public readonly int tableSize;

            public MyHashTable(int maxTableSize)
            {
                tableSize = maxTableSize;
                universe = new Node[tableSize];
            }
            public class Node
            {
                
                public int Key { get; set; }
                public object Value { get; set; }
                public Node Next { get; set; }
                public Node Previous { get; set; }
            }
            private int HashFuncation(int key)
            {
                int index = 7;
                int asciiVal = 0;
                for (int i = 0; i < key; i++)
                {
                    asciiVal = (int)key * i;
                    index = index * 31 + asciiVal;
                }
                return index % tableSize;
            }
            public void Insert(int key, object value)
            {
                int genIndex = HashFuncation(key);
                Node node = universe[genIndex];

                if (node == null)
                {
                    universe[genIndex] = new Node() { Key = key, Value = value };
                    return;
                }

                if (node.Key == key)
                    throw new Exception("Can't use same key!");

                while (node.Next != null)
                {
                    node = node.Next;
                    if (node.Key == key)
                        throw new Exception("Can't use same key!");
                }

                Node newNode = new Node() { Key = key, Value = value, Previous = node, Next = null };
                node.Next = newNode;
            }
            public object GetnthValue(int key)
            {
                int genIndex = HashFuncation(key);
                Node node = universe[genIndex];
                while (node != null)
                {
                    if (node.Key == key)
                    {
                        return node.Value;
                    }
                    node = node.Next;
                }

                throw new Exception("Don't have the key in hash!");
            }
           
        }

            static void Main(string[] args)
        {
            MyHashTable hashTable = new MyHashTable(50);
            hashTable.Insert(1, 5);
            hashTable.Insert(2, 6);
            hashTable.Insert(3, 7);
            hashTable.Insert(4, 8);

            

            Console.WriteLine("hash table");
            Console.WriteLine("1,5 -> 2,6 -> 3,7 -> 4,8");
            Console.WriteLine("Value of the nth node is: " + hashTable.GetnthValue(1));
            Console.ReadLine();
        }
    }