Domain Object Validation

For the sake of this framework, domain objects are defined as models (typically .NET classes) which contain state such as properties and/or fields. Domain object models relate to business-logic concepts and are free from technical/architectural concerns, particularly those related to user interface. The term "domain" borrows somewhat from Domain Driven Design but your application/team does not need to be following DDD; if you are then it matters not if these are entities, value objects or others.

Validated domain objects need not be limited to a single instance of a single class. CSF.Validation can validate complete graphs of related objects which are connected by associations such as properties.

A sample domain object to validate

Let's imagine that we are building an international e-commerce web application. One of its features is to purchase all of the items in the shopping cart. That request might be modelled using an object similar to the following.

public class PurchaseShoppingCartRequest
{
    public PostalAddress ShippingAddress { get; set; }
    public ICollection<LineItem> LineItems { get; set; }
}

public class PostalAddress
{
    public string StreetLine1 { get; set; }
    public string StreetLine2 { get; set; }
    public string CityOrTownName { get; set; }
    public string StateOrCountyName { get; set; }
    public string ZipOrPostalCode { get; set; }
    public long? CountryId { get; set; }
}

public class LineItem
{
    public long? ProductId { get; set; }
    public int Quantity { get; set; }
}

Now let's imagine some of the possibilities for validation:

• When validating the shipping address, the CountryId must not be null and must correspond to a country that is known-about by the application.
• When validating a ZIP or postal code there will be country-specific rules for the format of this value.
• Perhaps some products are not available in all countries. The object should be validated to verify that the selected product may be shipped to the selected country.

These rules are all non-trivial and would typically require the consumption of dependency-injected services. This is the sort of validation that CSF.Validation is well-suited to perform.