Where to validate individual properties when editing an existing entity?

Question

I'm using Entity Framework 6 and the repository pattern, with a service layer on top. In my POCO entity classes, I do use DataAnnotations for basic requirements such as KeyAttribute and RequiredAttribute. I perform business-specific validation in my service layer, though. So for example, my AccountService has an Insert method for inserting a new Account. I'll do checks like whether or not an account is eligible to be created based on some business rules, etc. If it's not eligible then I'll throw a validation exception there.

A problem that I'm trying to solve is what about when an existing Account is being updated? Where would I perform validation for changes to individual properties of Account? In my repository pattern implementation, I have a unit of work object which contains the DbContext and the unit of work class only exposes my individual services (which use that DbContext) as well as a single SaveChanges method, which just calls the DbContext's SaveChanges method. So, to update an existing Account, you would fetch it using the service layer, it'd be tracked by the DbContext and you'd edit the needed properties and call SaveChanges. There is no Edit method on my service that forces the user of my library to pass through that for validation.

Where should I perform this kind of validation?

Edit: I'd also be open to a way to make it so that some kind of Edit method is required, and that fetching existing entities does not track whem in the DbContext. I think this might complicate things such as lazy loading and stuff, though.

Answer 1

If you are already using DataAnnotations, look at implementing IValidatableObject

This will allow you to encapsulate the extended validation inside the class. There is an example of using it in this stackoverflow answer