Question

I have a viewModel I want to perform some more custom validation on.

I have made my viewModel to inherit from IValidatable and have some validation in:

public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
{

   ...

}

This works fine but I only want the validation for creates and not edits. I’m thinking the only way of doing this is some how determining within this method whether it is an edit or a create.

Is there a way of doing this or am I thinking aboout this whole thing incorrectly?

Answer 1

Use a separate view model for your create and insert actions. If your validation rules are that different, I think it would be worth it to use separate models anyway.

public class InsertMyObjectViewModel : IValidatable
{
    [Required]
    public string Name { get; set; }

    // note the lack of Required attribute here
    public string Address { get; set; }

    public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
    {
        ...
    }
}

And a separate for edit

public class UpdateMyObjectViewModel : IValidatable
{
    [Required]
    public string Name { get; set; }

    [Required]
    public string Address { get; set; }

    public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
    {
        ...
    }
}

This could make sense if your business rules dictate, for example, a customer’s name upon registration but not their address. However, when a user modifies their account, your business rules may require an address. It makes sense in a lot of cases to use a 1:1 viewmodel:action ratio per object.

Now, when you write your Validate logic, it becomes much simpler. There may be a bit of duplication, but it’s easier to modify when your business rules change in the future.