#823 – A Nested Factory Class Implemented as a Singleton

Below is an instance of the factory pattern, with the factory class nested within the class that it creates instances for, implemented as a singleton.

    public class Dog
    {
        public string Name { get; set; }

        private Dog(string name)
        {
            Name = name;
        }

        public class Factory
        {
            // Instance created when first referenced
            private static readonly Factory instance = new Factory();

            // Prevent early instantiation due to beforefieldinit flag
            static Factory() { }

            // Prevent instantiation
            private Factory() { }

            public static Factory Instance
            {
                get { return instance; }
            }

            // Factory method
            public Dog CreateDog(string name)
            {
                return new Dog(name);
            }
        }
    }