Adding association (link table record) without creating a new related record.

I have two tables Products and Categories with a many to many relationship. I am trying to copy the categories linked to one product (OriginalProduct) to another product (newProduct). The problem is when I execute the SaveChanges() method, I not only get the records in my linking table, but it also creates another copy of the categories in the categories table. I've tried this in many ways but here are the last couple that I've attempted:

 ' Copy Product/Categories
For Each oneProdCategory In Orig开发者_如何学编程inalProduct.Categories
  Dim relatedCategory = _productContext.GetObjectByKey(New EntityKey  ("ProductInfoEntities.Categories", "RecordId", oneProdCategory.RecordId))            
  Dim newCategory As New Category

  With newCategory
    .Description = relatedCategory.Description
    .isActive = relatedCategory.IsActive
    .RecordId = relatedCategory.RecordId
  End With

  newProduct.Categories.Add(newCategory)

Next

This attempt results in both linking table records being created (which is good) but is also creates copies of all the categories as well (not so good)

' Copy Product/Categories
For Each oneProdCategory In OriginalProduct.Categories
  Dim relatedCategory = _productContext.GetObjectByKey(New EntityKey ("ProductInfoEntities.Categories", "RecordId", oneProdCategory.RecordId))

  newProduct.Categories.Add(relatedCategory)

Next

This results in the following error:

"An entity object cannot be referenced by multiple instances of IEntityChangeTracker."

Edit

For Each oneProdCategory In OriginalProduct.Categories

  newProduct.Categories.Add(oneProdCategory)

Next


Private Sub tsBtnSave_Click(sender As System.Object, e As System.EventArgs) Handles tsBtnSave.Click 

   _productContext.SaveChanges()

   If _formMode = DataFormAction.Insert Or _formMode = DataFormAction.Duplicate Then
       Me.Close()         
   End If 
End Sub

---

You can try

newProduct.Categories.AddRange(OriginalProduct.Categories)

If your Categories property is a List OR

For Each oneProdCategory In OriginalProduct.Categories

  newProduct.Categories.Add(oneProdCategory)

Next

Make sure all the entities are retrieved, created with the same context.