I have some questions about Complex Criteria’s object

I have a interface (client) with multiples filters, per e.j: 

- Search by Code

- Search by Name

- Search by Last Name

- Search by ....

In these cases, I look with always the need of create a new Criteria object, per e.j.:

- SearchByCodeCriteria

- SearchByNameCriteria

- SearchByLastNameCriteria

- SearchBy....

A form of solution maybe create a class with this filters:

public class Filters

{

      string Code

      string Name

      string LastName

}

This class  may put in the constructor of any Criteria Object. But the problem is the same, I need always of conditionals, p.e.:

If (!String.NullOrEmpty(Foo.Code))

   Filters.Code = Foo.Code;

This same problem repeat been in the moment to fetch in the DataPortal:

If (!String.NullOrEmpty(Filters.Code))

   data = targetRepository.FetchByCode(Filters.Code);

If (!String.NullOrEmpty(Filters.Name))

   data = targetRepository.FetchByName(Filters.Name);

The questions is:

Exists any pattern for Criterias, similar to Specifications in DDD, I understand with CSLA .NET is not a ORM, but I think the conditionals in CSLA framework to Criterias Objects is a little problem.

Can you help me with any pattern?

P.D.: I use IoC and DI with Unity, also use Managed Extensibility Framework (MEF) with CSLA .NET to apply polymorphism, but my problem is when I need apply this concepts with the Criteria Objects.

Maybe an option:

public interface IDynamicList<T>

    {

        List<T> FindAllByCriteria(string criteria);

        List<T> FindAllByCriteria(Func<T, bool> criteria);

    }

 [Export(typeof(ICustomerRepository))]

    public class CustomerMock : ICustomerRepository

    {

        public List<Dto.CustomerDto> FindAllByCriteria(Func<Dto.CustomerDto, bool> criteria)

        {

            throw new NotImplementedException();

        }

    }

Best regards