LINQ Parent class queries db for fields in child class - vb.net

Question

I'm using EF 6.1.3 and .NET framework 4.5.2
I'm updating code which uses two classes:
Public Class Holder
<Key(), Column(Order:=0)>
Property Holder_No As Integer?
<Key(), Column(Order:=1)>
Property Title_No As Integer?
Property Family_Name As String
Property Given_Name_1 As String
Property Given_Name_2 As String
End Class
Public Class OwnerChange
Inherits Holder
Public Property Change_Type As String
Public Property Change_Date As Date
Public Property Process_Date As Date?
End Class
The Holder class is a 1:1 mapping with a table in the db.
The DbContext only creates a dbSet for the Holder class.
Public Property Holder As DbSet(Of Holder)
When I create a simple query to access data from the holder table in the db, I get column errors for change_type, change_date and process_date.
Using contextdb = New userContext()
Dim att1 = (From b In contextdb.Holder
Select b).Take(10)
End Using
The query seems to think I'm trying to query the parent table for the child class' information.
Why does LINQ request the child's columns from the parent class' table in the database? Do I need to do something to specify that I only want to retrieve the holder information?

Answer 1

The Entity Framework apparently creates a hierarchy whenever one class is inherited from another. So, when I was querying for the holder record, it was looking in the holder table for the elements from the OwnerChange class.
What I needed to do was take the holder class and turn it into an abstract class, then inherit it into the two classes I want to access different tables in the database.
Public MustInherit Class base_class
<Key(), Column(Order:=0)>
Property Holder_No As Integer?
<Key(), Column(Order:=1)>
Property Title_No As Integer?
Property Family_Name As String
Property Given_Name_1 As String
Property Given_Name_2 As String
End Class
Public Class OwnerChange
Inherits base_class
Public Property Change_Type As String
Public Property Change_Date As Date
Public Property Process_Date As Date?
End Class
Public Class holder
Inherits base_class
End Class
Changing the class hierarchy ultimately solved the problem.