EF: Validation failing on update when using lazy-loaded, required properties

I found the following post that had an answer for the same problem:

The cause of this problem is that in RC and RTM validation no longer lazy loads any properties. The reason this change was made is because when saving a lot of entities at once that have lazy loaded properties validation would get them one by one potentially causing a lot of unexpected transactions and crippling performance.

The workaround is to explicitly load all validated properties before saving or validating by using .Include(), you can read more on how to do this here: http://blogs.msdn.com/b/adonet/archive/2011/01/31/using-dbcontext-in-ef-feature-ctp5-part-6-loading-related-entities.aspx

My take on this is that is a pretty crappy proxy implementation. While unnecesarily walking the object graph and retriveing lazy-loaded properties is naturally something to be avoided (but apparently overlooked in Microsoft's first incarnation of EF), you shouldn't have to need to go un-proxying a wrapper to validate that it exists. On second thoughts, I'm not sure why you need to go walking the object graph anyway, surely the change tracker of the ORM knows what objects require validation.

I'm not sure why the problem exists, but I'm sure I wouldn't be having this problem if I was using say, NHibernate.

My 'workaround' - What I've done is define the Required nature of the relationship in a EntityTypeConfiguration class, and removed the Required attribute. This should make it work fine. It means that you will not validate the relationship, but it will fail the update. Not an ideal result.

Ok, here is the real answer =)

First a little explanation

if you have a property (like your Bar) noting a FK (ForeignKey), you can also have the corresponding FK field in your model so if we only need the FK and not the actual Bar we don't need it to go to the database:

[ForeignKey("BarId")]
public virtual Bar Bar { get; set; }
public int BarId { get; set; }

Now, to answer your question, what you can do to make the Bar as Required is to flag the BarId property as required, but not the Bar itself:

[ForeignKey("BarId")]
public virtual Bar Bar { get; set; }
[Required] //this makes the trick
public int BarId { get; set; }

this works like a charm =)

Transparent workaround to ignore error on unloaded references

In your DbContext, override ValidateEntity method to remove validation error on references that are not loaded.

    private static bool IsReferenceAndNotLoaded(DbEntityEntry entry, string memberName)
    {
        var reference = entry.Member(memberName) as DbReferenceEntry;
        return reference != null && !reference.IsLoaded;
    }

    protected override DbEntityValidationResult ValidateEntity(DbEntityEntry entityEntry,
                                                 IDictionary<object, object> items)
    {
        var result = base.ValidateEntity(entityEntry, items);
        if (result.IsValid || entityEntry.State != EntityState.Modified)
        {
            return result;
        }
        return new DbEntityValidationResult(entityEntry,
            result.ValidationErrors
                  .Where(e => !IsReferenceAndNotLoaded(entityEntry, e.PropertyName)));
    }

Pros :

• Transparent and will not crash when you use inheritance, complex types, doesn't require modification on your model...
• Only when validation fails
• No reflection
• Iterates only on invalid unloaded references
• No useless data loading

Here's a semi-acceptable work-around:

var errors = this.context.GetValidationErrors();
foreach (DbEntityValidationResult result in errors) {
    Type baseType = result.Entry.Entity.GetType().BaseType;
    foreach (PropertyInfo property in result.Entry.Entity.GetType().GetProperties()) {
        if (baseType.GetProperty(property.Name).GetCustomAttributes(typeof(RequiredAttribute), true).Any()) {
            property.GetValue(result.Entry.Entity, null);
        }
    }
}