Estou com alguns problemas ao usar o EF com o AutoMapper. = /

por exemplo

Tenho duas entidades relacionadas (clientes e pedidos) e são classes de DTO:

class CustomerDTO
{
   public string CustomerID {get;set;}
   public string CustomerName {get;set;}
   public IList< OrderDTO > Orders {get;set;}
}<p></p>

<p>class OrderDTO
{
   public string OrderID {get;set;}
   public string OrderDetails {get;set;}
   public CustomerDTO Customers {get;set;}
}</p>

<p>//when mapping Entity to DTO the code works
Customers cust = getCustomer(id);
Mapper.CreateMap< Customers, CustomerDTO >();
Mapper.CreateMap< Orders, OrderDTO >();
CustomerDTO custDTO = Mapper.Map(cust);</p>

//but when i try to map back from DTO to Entity it fails with AutoMapperMappingException.
Mapper.Reset();
Mapper.CreateMap< CustomerDTO , Customers >();
Mapper.CreateMap< OrderDTO , Orders >();
Customers customerModel = Mapper.Map< CustomerDTO ,Customers >(custDTO); // exception is thrown here



Am I doing something wrong?

Thanks in Advance !