namespace Factory

{

    public interface IPerson

    {

    }

}

namespace Factory

{

    public class Student : IPerson

    {

    }

     public class Worker : IPerson

    {

    }

}

 <appSettings>

    <add key="factoryConfig" value="Factory,Factory.Student"/>

  </appSettings>

namespace Factory

{

    public class Factory

    {

        private static string factoryConfig = ConfigurationManager.AppSettings["factoryConfig"];

        public static IPerson CreateInstance()

        {

            IPerson iPerson = null;

            try

            {

                string assemblyName = factoryConfig.Split(',')[];

                string typeName = factoryConfig.Split(',')[];

                iPerson = (IPerson)Activator.CreateInstance(assemblyName, typeName).Unwrap();

            }catch(Exception e){

                throw e;

            }

            return iPerson;

        }

    }

}