In chapter five, the book demostrates Hashtables using the Structure Demo program. I don't entirely understand the function of one property within the CustomerCollection class:

    Public ReadOnly Property EmailHashtable() As Hashtable
        Get
            Return _emailHashtable
        End Get
    End Property

I tried removing the property and replacing EmailHashtable with _emailHashtable in the rest the code and program continued to work exactly as it did before:

Public Class CustomerCollection
    Inherits System.Collections.CollectionBase
    Private _emailHashtable As New Hashtable

    Public Shadows Sub Clear()
        MyBase.Clear()
        _emailHashtable.Clear()
    End Sub

    Public Shadows Sub RemoveAt(ByVal index As Integer)
        Remove(Item(index))
    End Sub

    Public Sub Add(ByVal newCustomer As Customer)
        Me.List.Add(newCustomer)
        _emailHashtable.Add(newCustomer.Email.ToLower, newCustomer)
    End Sub

    Public Sub Remove(ByVal removeCustomer As Customer)
        Me.List.Remove(removeCustomer)
        _emailHashtable.Remove(removeCustomer.Email.ToLowe r)
    End Sub

    Default Public Property Item(ByVal index As Integer) As Customer
        Get
            Return Me.List.Item(index)
        End Get
        Set(ByVal Value As Customer)
            Me.List.Item(index) = Value
        End Set
    End Property

    Default Public ReadOnly Property Item(ByVal email As String) As Customer
        Get
            Return _emailHashtable.Item(email.ToLower)
        End Get
    End Property
End Class

I guess the Property could later on take on additonal code that could give it some special functionality, making the code easier to maintain? The book doesn't really talk about it either way.

You are correct in your assumptions. The EmailHashtable property is used internally in the CustomerCollection class but has been defined as public so it could be used by a consumer of this class to get the entire email hash table.

The original author did not explain this well nor did they provide an example of using this property from the code in the form.

Thearon