Random username generator

Program.cs

static void Main(string[] args)
        {
            string username = ChooseRandomAdjective() + ChooseRandomNoun();
            Console.WriteLine(username);  username = ChooseRandomAdjective() + ChooseRandomNoun();
            Console.WriteLine(username);  username = ChooseRandomAdjective() + ChooseRandomNoun();
            Console.WriteLine(username);  username = ChooseRandomAdjective() + ChooseRandomNoun();
            Console.WriteLine(username);  username = ChooseRandomAdjective() + ChooseRandomNoun();
            Console.WriteLine(username);  username = ChooseRandomAdjective() + ChooseRandomNoun();
            Console.WriteLine(username);
            Console.ReadLine();
        }

        static string ChooseRandomAdjective()
        {
            Random randomAdjective = new Random();
            int num = randomAdjective.Next(1, 11);

            string a = "";

            switch (num)
            {
                case 1:
                    a = "Sweet";
                    break;
                case 2:
                    a = "Cubic";
                    break;
                case 3:
                    a = "Big";
                    break;
                case 4:
                    a = "Rainy";
                    break;
                case 5:
                    a = "Cold";
                    break;
                case 6:
                    a = "Dark";
                    break;
                case 7:
                    a = "Black";
                    break;
                case 8:
                    a = "Long";
                    break;
                case 9:
                    a = "Electric";
                    break;
                case 10:
                    a = "Short";
                    break;
                default:
                    a = "Error";
                    break;
            }

            return a;
        }

        static string ChooseRandomNoun()
        {
            Random randomNoun = new Random();
            int num = randomNoun.Next(1, 11);

            string n = "";

            switch (num)
            {
                case 1:
                    n = "Dog";
                    break;
                case 2:
                    n = "Tree";
                    break;
                case 3:
                    n = "Doctor";
                    break;
                case 4:
                    n = "Truth";
                    break;
                case 5:
                    n = "Happiness";
                    break;
                case 6:
                    n = "Neighbor";
                    break;
                case 7:
                    n = "Instrument";
                    break;
                case 8:
                    n = "Phone";
                    break;
                case 9:
                    n = "Piano";
                    break;
                case 10:
                    n = "Rain";
                    break;
                default:
                    n = "Error";
                    break;
            }

            return n;
        }