Question

I’m building a MVC application which is a bit more complex than what I usually do and I want to try a new class structure. Basically theres a lot of reading going on. Just 5-10% of operations will be insert/update against the database.

Because of this, I’m thinking of creating base DTO classes which would be returned from a database layer. Then, business objects would inherit from the DTO class in order to extend the basic structure with all the validation and business rules.

Example:

namespace Project.DTO
{
    public class Employee
    {
        public string Name;
        public string Surname;
        ...
    }
}

namespace Project
{
    public class Employee : Project.DTO.Employee
    {
        public bool IsValid()
        {
        ...
        }
    }
}

Is this a good approach? What I haven’t thought off yet is how to use them inside the MVC, as the “correct” way would be to implement model classes. I believe I could create model classes that inherited from the DTO objects as well… but I’m unsure.

I would also need a way to handle all validation functions with some kind of Interface, as to avoid repeating to much generic code on the GUI.

Thanks in advance!

Answer 1

I would probably use a completely different approach. My primary thoughts are these:

• I would like looser coupling between the classes, so I would not have my model classes inherit from my DTO objects
• I would probably not include validation logic in my model classes

This would lead to the following structure to start with:

namespace Project.DTO
{
    public class Employee
    {
        public string Name;
        public string Surname;
        ...
    }
}

namespace Project
{
    public class Employee
    {
        public string Name { get; set; }
        public string Surname { get; set; }
    }
}

When it comes to the validation logic, I would make an interface for the validation logic, that is injected into the Emplyee class:

public interface IValidator<T>
{
    bool IsValid(T objectToInspect);
}
public class Employee
{
    private readonly IValidator<Employee> validator;
    public Employee(IValidator<Employee> validator)
    {
        this.validator = validator;
    }

    public string Name { get; set; }
    public string Surname { get; set; }

    public bool IsValid()
    {
        return validator.IsValid(this);
    }
}

This opens up your design for a whole range of features, including using IoC containers and better support for testing.