bookhashtable.vb

编程之道VB.NETt程序设计入门-589M.zip

Public Class BookHashTable
    Inherits Hashtable

    '用Shadows关键字完全屏蔽基类的Add方法和Item属性
    '使得在BookHashTable中放入其它类型数据的企图
    '没有办法通过编译

    Public Shadows Sub Add(ByVal key As Object, ByVal value As Book)
        MyBase.Add(key, value)
    End Sub

    Public Shadows Property Item(ByVal key As Object) As Book
        Get
            Return CType(MyBase.Item(key), Book)
        End Get
        Set(ByVal Value As Book)
            MyBase.Item(key) = Value
        End Set
    End Property

End Class