Shared - Understanding Access Modifiers In .Net With List ( Of Object)?

I've recently been updating a lot of my code to comply with proper n-tier architecture and OO programming, following examples from a book.I'm starting to get problems now because I don't fully understand the access modifiers.If I run the following code I get an error at the line

Dim clientFamilyDataAccessLayer As New ClientFamilyDAO

in the BLL at the point it creates an instance of the DAL. The full error message is: "The type initializer for 'ClientFamilyDAO' threw an exception. ---> System.NullReferenceException: Object reference not set to an instance of an object."

How do I use these function to create a list of ClientFamily objects that I can then work with?On my UI layer I'm creating a list of objects; ClientFamilies

Dim listOfClientFamilies As List(Of ClientFamily) = ClientFamily.GetClientFamiliesByKRM(selectedEmployee.StaffNumber)

This is the function in the BLL

Public Shared Function GetClientFamiliesByKRM(ByVal krmStaffNumber As Integer) As List(Of ClientFamily)
Dim clientFamilyDataAccessLayer As New ClientFamilyDAO
Return clientFamilyDataAccessLayer.GetClientFamiliesByKRM(krmStaffNumber)
End Function

and this is function in the DAL

Public Function GetClientFamiliesByKRM(ByVal staffNumber As Integer) As List(Of ClientFamily)
Dim currentConnection As SqlConnection = New SqlConnection(_connectionString)
Dim currentCommand As New SqlCommand

[code]....