Question

我试着获得每张专辑的歌曲列表。我创建了2个类：专辑＆amp;宋，所以我可以像下面一样组织它们：

Public Class Album
    Sub New()
        Entered = Now
    End Sub
    Public Entered As DateTime
    Public AlbumName As String = ""
    Public Artist As String = ""
    Public YearReleased As Integer = 1900
    Public Songs As New List(Of Song)
End Class

Public Class Song
    Public SongName As String = ""
    Public SongLength As String = ""
End Class

但是，当我将歌曲添加到专辑时，我总是会输入最后一首歌曲。这是一个输出结果的例子。

Protected Sub Test()
    Dim vAlbum As New Album
    Dim vsong As New Song

    vAlbum.AlbumName = "Test 01"
    vAlbum.Artist = "Jackie"
    vAlbum.YearReleased = 2012

    vsong.SongName = "Exit"
    vsong.SongLength = "1.5"
    vAlbum.Songs.Add(vsong)

    vsong.SongName = "Exit II"
    vsong.SongLength = "2.5"
    vAlbum.Songs.Add(vsong)

    For Each sSong As Song In vAlbum.Songs
        Response.Write(sSong.SongName + "<br>")
    Next
End Sub

输出：

退出II

我到处都是谷歌，但找不到onyl，所有歌曲的最新记录都显示出来。

欢迎任何帮助。

谢谢，弗雷德

Answer 1

经典参考问题。你的vsong总是同一个对象。您需要实例化一个新实例：

...
vAlbum.Songs.Add(vsong)
vsong = new Song()
vsong.SongName = "Exit II"
...

Answer 2

您要添加相同的Song两次，只需更改其字段。

你应该使用这样的东西：

Dim vAlbum As New Album

vAlbum.AlbumName = "Test 01"
vAlbum.Artist = "Jackie"
vAlbum.YearReleased = 2012

Dim vsong As New Song
vsong.SongName = "Exit"
vsong.SongLength = "1.5"
vAlbum.Songs.Add(vsong)

vsong As New Song ' create a new instance of Song
vsong.SongName = "Exit II"
vsong.SongLength = "2.5"
vAlbum.Songs.Add(vsong)

或更好，使用对象初始值设定项或创建一个取得所有必要值的构造函数：

Public Class Song

    Public SongName As String = ""
    Public SongLength As String = ""

    Public Sub new(name as String, length as String)
        SongName = name
        SongLength = length
    End Sub

End Class

...

vAlbum.Songs.Add(new Song("Exit", "1.5"))
vAlbum.Songs.Add(new Song("Exit II", "2.5"))

VB / CLASS问题：只显示所有记录的最后一条记录

2 个答案: