Multiple sets of Validation in Entity Framework - entity-framework

Question

I came across this problem where I should allow different sets of validation when saving a model. Usually the validation depends on how the user wants to save the data. For example, if the user wants to save his data as "Draft", I should allow some fields to be blank. If not "Draft", I should put more restrictions.
class Form
{
public int ID { get; set; }
[Required("Title is required.")]
public string Title { get; set; }
[Required("Body is required.")]
public string Body { get; set; }
public bool IsDraft { get; set; }
}
In the code above, I want the validation for body to work only if IsDraft is false.
How do you create multiple sets of validation? Or how to properly create conditional validation in Entity Framework?

Answer 1

Data annotations are not only used for validation but also to make your code in sync with the database. I.e. in EF Code First, if you remove Required field, then your database must allow NULL to be inserted in matching column.
Therefore you can do the following approach:
Create your entity model class to have as lowest requirements as possible
Create your view/DTO model class that will implement IValidatableObject interface
Implement IValidatableObject interface and do conditional validation there
IValidatableObject interface allows your class to be used by Validator (MSDN on Validator) from System.ComponentModel.DataAnnotations namespace, in the same way the validation is done via annotation attributes.
Interface implementation should look like this:
public class FormDto: IValidatableObject
{
public int ID { get; set; }
[Required("Title is required.")]
public string Title { get; set; }
[Required("Body is required.")]
public string Body { get; set; }
public bool IsDraft { get; set; }
public IEnumerable<ValidationResult> Validate(ValidationContext validationContext)
{
if(!IsDraft && string.IsNullOrWhiteSpace(Body)) yield return new ValidationResult("Body is required.", new string [] {"Body"});
if(!IsDraft && string.IsNullOrWhiteSpace(Title)) yield return new ValidationResult("Title is required.", new string [] {"Title"});
}
}
If your view / DTO model is going through i.e. MVC pipeline, this interface will be invoked automatically. If from any reason you notice it is not invoked (I don't know the structure of your solution), you can plug this code somewhere in your process pipeline and it will invoke validation / throw exception:
public static class IValidatableObjectExtensions
{
public static void SelfValidate(this IValidatableObject model)
{
ValidationContext ctx = new ValidationContext(model);
Validator.ValidateObject(model, ctx, true);
}
}