using System;

public class Program

{

    public static void Main()

    {

        /// BEGIN - convert a customer entity

        QuickBooksCustomer qbCustomer = new QuickBooksCustomer() { Name = "John Smith" };

        Customer ourAppEntity = ConvertEntity(qbCustomer) as Customer;

        Console.Write(ourAppEntity.CustomerName);

        /// END - convert a customer entity

    }               

    //service factory

    public static ISyncService Create(Type qbEntityType)

    {

        Console.WriteLine("qbEntity type in Factory: " + qbEntityType.ToString());

        if(qbEntityType == typeof(QuickBooksCustomer))

        {

            Console.WriteLine("qbEntity is QuickBooksCustomer, return CustomerSyncService.");

            var service = new CustomerSyncService();   

            return service; 

        }

        if(qbEntityType == typeof(QuickBooksVendor))

        {

            return new VendorSyncService();    

        }

        throw new Exception("Invalid Type");        

    }

    //converts quickbooks entity to our app's entity

    public class CustomerSyncService : ISyncService

    {

        public IEntity ConvertQBEntityToAppEntity(IQBEntity qbCustomer)

        {

            return new Customer(){ 

                Id = 0,

                CustomerName = qbCustomer.Name 

            };  

        }

    }   

    //converts quickbooks entity to our app's entity

    public class VendorSyncService : ISyncService

    {

        public IEntity ConvertQBEntityToAppEntity(IQBEntity qbVendor)

        {

            return new Vendor(){ 

                Id = 0,

                VendorName = qbVendor.Name 

            };  

        }

    }   

    //generic conversion method

    public static object ConvertEntity(IQBEntity qbEntity)

    {

        Console.WriteLine("qbEntity type to call Factory with: " + qbEntity.GetType().ToString());

        //call factory to create correct entity conversion service

        var service = Create(qbEntityType: qbEntity.GetType());

        if(service == null) Console.WriteLine("Service Factory returned null!!!");

        //call conversion service, supply quickbooks entity, return our app's entity

        var entity = service.ConvertQBEntityToAppEntity(qbEntity);

        return entity;

    }

}

​

//quickbooks IEntity

public interface IQBEntity {

    string Name { get; set; }

}

​

//our app's IEntity

public interface IEntity {

    int Id { get; set; }

}

​

public interface ISyncService

{

    IEntity ConvertQBEntityToAppEntity(IQBEntity qbEntity);

}

​

//quickbooks customer entity

public class QuickBooksCustomer: IQBEntity{

    public string Name { get; set; }

    //...other properties

}

​

//our app's customer entity

public class Customer: IEntity{

    public int Id { get; set; }

    public string CustomerName { get; set; }

    //...other properties

}

​

//quickbooks vendor entity

public class QuickBooksVendor: IQBEntity{

    public string Name { get; set; }

    //...other properties

}

​

//our app's vendor entity

public class Vendor: IEntity{

    public int Id { get; set; }

    public string VendorName { get; set; }

    //...other properties

}