Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Console.WriteLine(DateTime.Now)
        cfg = New Configuration()

        cfg.AddAssembly("classes")

        factory = cfg.BuildSessionFactory()

        session = factory.OpenSession()

        bindSrc = New BindingSource

        DataGridView1.AutoGenerateColumns = False
        bindSrc.Add(New DOrderDetails())
        DataGridView1.DataSource = bindSrc
        Dim column As DataGridViewColumn

        column = New DataGridViewCheckBoxColumn()
        column.Name = "DEL"
        DataGridView1.Columns.Add(column)

        column = New DataGridViewTextBoxColumn()
        column.DataPropertyName = "pOR_NO"
        column.Name = "Order No"
        DataGridView1.Columns.Add(column)

        column = New DataGridViewTextBoxColumn()
        column.DataPropertyName = "pDESC"
        column.Name = "Description"
        DataGridView1.Columns.Add(column)

End Sub

Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim x As DOrderDetails= DirectCast(bindSrc.Item(DataGridView1.SelectedCells(0).RowIndex), DOrderDetails)

        Console.WriteLine(x.pOrderDetails_ID.pOR_LINE)   '<------------------Error here
    End Sub

Imports System

Namespace Dialogue
    Public Class DOrderDetails
        Dim _OrderDetails_ID As DOrderDetails_ID
        Dim _DESC As String
        Dim _PRICE As Decimal
        Dim _QTY As Integer

        Public Sub New()
            _OrderDetails_ID = New DOrderDetails_ID
        End Sub

        Public Overridable Property pOrderDetails_ID() As DOrderDetails_ID
            Get
                Return _OrderDetails_ID
            End Get
            Set(ByVal value As DOrderDetails_ID)
                _OrderDetails_ID = value
            End Set
        End Property
        Public Overridable Property pDESC() As String
            Get
                Return _DESC
            End Get
            Set(ByVal value As String)
                _DESC = value
            End Set
        End Property
        Public Overridable Property pPRICE() As Decimal
            Get
                Return _PRICE
            End Get
            Set(ByVal value As Decimal)
                _PRICE = value
            End Set
        End Property
        Public Overridable Property pQTY() As Integer
            Get
                Return _QTY
            End Get
            Set(ByVal value As Integer)
                _QTY = value
            End Set
        End Property
    End Class

    Public Class DOrderDetails_ID
        Dim _OR_NO As String
        Dim _OR_LINE As Integer

        Public Overridable Property pOR_NO() As String
            Get
                Return _OR_NO
            End Get
            Set(ByVal value As String)
                _OR_NO = value
            End Set
        End Property
        Public Overridable Property pOR_LINE() As Integer
            Get
                Return _OR_LINE
            End Get
            Set(ByVal value As Integer)
                _OR_LINE = value
            End Set
        End Property

        Public Overloads Overrides Function Equals(ByVal Obj As Object) As Boolean
            Dim x As DOrderDetails_ID = DirectCast(Obj, DOrderDetails_ID)

            Return Me.pOR_LINE = x.pOR_LINE And Me.pOR_NO = x.pOR_NO
        End Function

        Public Overloads Overrides Function GetHashCode() As Integer

            Return New Random().Next()

        End Function
    End Class
End Namespace

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2">
   <class name="Dialogue.DOrderDetails, classes" table="orderdetails">
      <composite-id name="pOrderDetails_ID" class="Dialogue.DOrderDetails_ID, classes">
         <key-property name="pOR_NO" column="OR_NO" type="String"/>
         <key-property name="pOR_LINE" column="OR_LINE" type="Int32"/>
      </composite-id>
      <property name="pDESC" column="DESC" type="String"/>
      <property name="pPRICE" column="PRICE" type="Decimal"/>
      <property name="pQTY" column="QTY" type="Int32"/>
   </class>
</hibernate-mapping>