Public Class CartItem
    Public ID As String
    Public Name As String
    Public Price As Double
    Public Count As Integer

    Public Sub New()
        ID = "-1"
        Name = ""
        Price = 0
        Count = 0
    End Sub
End Class

Public Class ShoppingCart
    Public Items As New Hashtable

    Public Sub New()
        Items.Clear()
    End Sub

    'Add an item to the Shopping Cart
    Public Function Add(ByVal c As CartItem) As Boolean
        Dim tmpItem As CartItem

        If c.Name <> "" And c.Count > 0 Then
            tmpItem = Items(c.Name)
            If Not tmpItem Is Nothing Then
                tmpItem.Count += c.Count
            Else
                Items.Add(c.Name, c)
            End If
            Return True
        Else
            Return False
        End If
    End Function

    'Modify an object quantity
    'If quantity is zero the item is removed
    Public Function Modify(ByVal c As CartItem) As Boolean
        Dim tmpItem As CartItem
        If c.Name <> "" Then
            tmpItem = Items(c.Name)
            If Not tmpItem Is Nothing Then
                If tmpItem.Count > 0 Then
                    tmpItem.Count = c.Count
                Else
                    Items.Remove(c.Name)
                End If
                Return True
            Else
                Return False
            End If
        Else
            Return False
        End If
    End Function

    'Empty the Shopping Cart
    Public Sub Empty()
        Items.Clear()
    End Sub

    'calculate an object total price (items*price)
    Public Function ItemTotal(ByVal itemName As String) As Double
        Dim tmpItem As CartItem
        If itemName <> "" Then
            tmpItem = Items(itemName)
            If Not tmpItem Is Nothing Then
                Return tmpItem.Count * tmpItem.Price
            Else
                Return 0.0
            End If
        Else
            Return 0.0
        End If
    End Function

    'Calculate the total price to pay
    Public Function Total() As Double
        Dim totale As Double = 0.0
        For Each k As String In Items.Keys
            Dim ci As CartItem = Items(k)
            totale += ci.Price * ci.Count
        Next
        Return totale
    End Function
End Class