Implementing a Factory Pattern in C#

I am implementing a factory pattern and would like to get it confirmed that it is the right approach. Is there any error in this approach. If so where should i be making the changes.

First I am creating an interface IAuto.

 //IAuto.cs
    namespace TestDesignPatterns.Auto
    {
        public interface IAuto
        {

            void start();
            void stop();
        }
    }

Create a class that implements the IAuto.

    //clsBMW.cs
    namespace TestDesignPatterns.Auto
    {
        public class clsBMW : IAuto
        {
            public void start()
            {
                Console.WriteLine("BMW started");
            }

            public void stop()
            {
                Console.WriteLine("BMW stopped");
            }
        }
    }

Create another concrete class for Audi implementing IAuto.

namespace TestDesignPatterns.Auto
{
    public class clsAudi : IAuto
    {
        public void start()
        {
            Console.WriteLine("Audi started");
        }

        public void stop()
        {
            Console.WriteLine("Audi stopped");
        }
    }
}

Create an Interface of factory which creates the model.

//IautoFactory.cs
public interface IAutoFactory
    {
       IAuto createModel(ModelType m);
    }

concrete factory class.

//clsAutofactory.cs
 public class clsAutoFactory : IAutoFactory
    {
        public IAuto createModel(ModelType m)
        {
            IAuto instance = null;
            switch (Convert.ToInt32(m))
            {
                case 0:
                    instance = new clsBMW();
                    break;

                case 1:
                   instance =  new clsAudi();
                    break;
                default:
                    break;


            }

            return instance;
        }
    }

Main Program

//program.cs

            IAutoFactory factory = new clsAutoFactory();
            IAuto model = factory.createModel(ModelType.Audi);
            model.start();
            model.stop();
            Console.ReadKey()