Entity Framework and 2 associations on the same table. Is it possible? - entity-framework

Question

I have 3 tables:
Product
Category
ProductCategory
when doing entity framework Database First it creates 2 classes.
Product {
int ProductId
virtual ICollection<Category>
}
Categories {
int CategoryId
virtual ICollection<Product>
}
this is great.
I want to create a new property on the table ProductCategory, for example, CreateDate
So I will have one more entity (ProductCategory) with the CreateDate property :
Product
Category
ProductCategory
So far so good, but it removes the navegability from Product to Category and creates the navegability from Product to ProductCategory and then to Category.
I manually changed in model browser and added a new navegability that create the previous behaviour in classes so I ended up with what I want :
Product {
int ProductId
virtual ICollection<Category>
ProductCategory
}
Category {
int CategoryId
virtual ICollection<Product>
ProductCategory
}
ProductCageory {
Product
Category
}
all compiles fine, but when I run the code and update an entity the following error raises :
error 3034: Problem in mapping fragments starting at lines 2445, 2452:
Two entities with possibly different keys are mapped to the same row.
Ensure these two mapping fragments map both ends of the AssociationSet
to the corresponding columns.
Is there any way to keep my desired scenario (Both navegabilities from Product to ProductCategory and to Category and vice versa) ? If so, how can I get rid of this error ? am I missing mapping something ?
Tryied to be the less verbose possible but I don't mind adding more information or updating the question if anything missing so don't hesitate to ask for more info. Thanks.
Extra: Using MySql 6.8.3 with Entity Framework 6 (latest minus version) Database First using DbContext and T4.
updated:
This is what I want to have :
public class Product
{
public int Id { get; set; }
public ICollection<ProductCategory> ProductCategories { get; set; }
public ICollection<Category> Categories { get; set; }
}
public class Category
{
public int Id { get; set; }
public ICollection<ProductCategory> ProductCategories { get; set; }
public ICollection<Product> Products { get; set; }
}
public class ProductCategory
{
public int Id { get; set; }
public int ProductId { get; set; }
public Product Product { get; set; }
public int CategoryId { get; set; }
public Category Category { get; set; }
}

Answer 1

If you want to have many to many relationship that can navigate both ways, you should have as follow.
public class Product
{
public int Id { get; set; }
public ICollection<ProductCategory> ProductCategories { get; set; }
[NotMapped]
public ICollection<Category> Categories
{
get { return (ProductCategories ?? new ProductCategory[0]).Select(pc => pc.Category).ToArray(); }
}
}
public class Category
{
public int Id { get; set; }
public ICollection<ProductCategory> ProductCategories { get; set; }
[NotMapped]
public ICollection<Product> Products
{
get { return (ProductCategories ?? new ProductCategory[0]).Select(pc => pc.Product).ToArray(); }
}
}
public class ProductCategory
{
public int Id { get; set; }
public int ProductId { get; set; }
public Product Product { get; set; }
public int CategoryId { get; set; }
public Category Category { get; set; }
}