Validation performed too many times?

I have a strange situation here.

I have some extra validation code on an entity. When I add a parent reference to it before saving, and if my entity is not valid, I get 3 error messages for the same thing.

It's more easy for me to explain with simple code example:

--------------------
// additional validation in Product Entity
public partial Class Product
{
        protected override void OnValidate()
        {
            CheckProductNameValidity();
        }

        private void CheckProductNameValidity()
        {
            DataModelUnitOfWork work = this.UnitOfWork;

            var query = from p in work.Products
                             where p.Name == this.Name
                            select p;
            if (query.Count() > 0)
            {
                this.Errors.AddError("Product already exists");
            }
        }
}

Test Method
{
...
                ProductType prodType = (from p in context.ProductType
                                         where p.Code == 100
                                         select p).Single();

                Product prod= new Product();
                prod.Name = "LightSpeed";
                prod.ProductType = prodType;

                context.Add(prod);

                bool validStatus = prod.IsValid;

                 if (validStatus )
                {
                    context.SaveChanges();
                }
                else
                {
                    System.Diagnostics.Debug.WriteLine(prod.Errors);
                }
...
}
-----------------------
When I run the TestMethod, in the Errors list for the product item I would get 2 same messages and 1 which is actually also referencing to the same error:
1) "Product already exists"
2) "Product type is invalid" (because of "Products item 0 is invalid", which is the product item itself for which I issued the validation check)
3) "Product already exists"

I looked a bit in Debug mode, OnValidate for Product triggers twice (guessing probably doing 1st check for Product itself, and afterward second check via reference validation on Product type).

Strange behaviour, IMHO.

P.S.
Of course, if I change the code to assign product type by Id
---------
prod.ProductTypeId = prodType.Id;
---------
I would get only one message "Product already exists"

Thanks for alerting us to this.  We've reproduced the problem and will look into it.

This is now fixed and you can get the fix in the current nightly build.  You can get Express edition nightlies from the Downloads tab, and Standard or higher edition nightlies from the store.  Thanks again for alerting us to this.

Ok, thanks. I can confirm it also now works properly on my original testing example.

BTW, just persuading my manager to open the bag and get the Enteprise license. Hopefuly next week... :)