c# - 类修饰符

Question

我从来没有主动学习过正确的类修饰符，因为它一直是“拥有很好”而不是“必须拥有”。

令我烦恼的是我可以做 Dim F as New Person.FavoriteFoodsList。

我应该使用哪个类修饰符才能使我的 Person 类可以使用 FavoriteFoodsList 但 Person 之外的任何东西都不能实例化 FavoriteFoodsList？

Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
    Dim P As New Person
    P.FavoriteFoods.Add("Pizza")
    Dim F As New Person.FavoriteFoodsList 'How do I prevent this
End Sub
Public Class Person
    Public FavoriteFoods As New FavoriteFoodsList
    Public Class FavoriteFoodsList
        Inherits Collections.Generic.List(Of String)
    End Class
End Class

Answer 1

我建议您为您的类定义一个公共(public)接口(interface)，然后将实现标记为私有(private)。

Public Interface IFavoriteFoodsList
    Inherits Collections.Generic.IList(Of String)
    ' Define other public api methods'
End Interface

Public Class Person
    Public FavoriteFoods As IFavoriteFoodsList = New FavoriteFoodsList
    Private Class FavoriteFoodsList
        Inherits Collections.Generic.List(Of String)
        Implements IFavoriteFoodsList
    End Class
End Class