Private Sub CreateConstraint(dataSet As DataSet)
    ' Create the ForignKeyConstraint with two DataColumn objects.
    Dim parentCol As DataColumn = _
       dataSet.Tables("Customers").Columns("id")
    Dim childCol As DataColumn = _
       dataSet.Tables("Orders").Columns("OrderID")
    Dim fkeyConstraint As _
       New ForeignKeyConstraint("fkConstraint", parentCol, childCol)

    ' Test against existing members using the Equals method.
    Dim testConstraint As ForeignKeyConstraint
    For Each testConstraint In  dataSet.Tables("Orders").Constraints
        If fkeyConstraint.Equals(testConstraint) Then
            Console.WriteLine("Identical ForeignKeyConstraint!")
            ' Insert code to delete the duplicate object, 
            ' or stop the procedure.
        End If
    Next testConstraint
End Sub