如何排序结构数组？

-1

我有一个结构数组。它是这样宣称的如何排序结构数组？

Public SongsList as New List(Of Song)

“宋”它的结构的名称。它有2个变量：路径和名称; 我想知道如何按名称排序这个数组。

Public Structure Song 
    Public Path as String 
    Public Name as String 
End Structure

我想这

ListBox1.Items.Clear() 
Dim sorted = SongsList.OrderBy(Function(s) s.Name).ToList 
Dim i As Integer 
For i = 0 To sorted.Count - 1 
    ListBox1.Items.Add(sorted(i).Name.ToString) 
Next

但它抛出一个NullReferenceException。

这是我如何将项目添加到SongsList

Dim open As New OpenFileDialog 
open.Title = "Add songs" 
open.Filter = "MP3 Files(*.mp3)|*.mp3" 
open.Multiselect = True 
ListBox1.Items.Clear() 
If open.ShowDialog = DialogResult.OK Then 
    For Each SelectedSong As String In open.FileNames 
     i += 1 
     Dim songToAdd As New Song 
     songToAdd.Path = SelectedSong.ToString 
     songToAdd.Name = GetSafeFileName(SelectedSong.ToString) 
     SongsList.Add(songToAdd) 
     ListBox1.Items.Add(SongsList(i).Path) 
    Next 
End If

来源

2015-09-25 Cosmin Stoian

我编辑了你的q可以在OneFineDay的答案的评论中加入你提到的代码;但请下一次尝试包含您尝试过的代码 - 即使它不起作用。现在，你能告诉我们如何填写'SongsList'吗？ –

为什么你在已经是字符串的变量上调用'.ToString'？ – Enigmativity

重复的[什么是NullReferenceException，我该如何解决它？]（http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it） –

可以使用Lambda表达式。它使用您在OrderBy函数中选择的字段。让我们覆盖ToString方法来告诉列表框显示什么，然后你可以将列表设置为数据源。

类：

Public Class Song 
    Public Property Path as String 
    Public Property Name as String 
    Public Overrides Function ToString() As String 
    Return Me.Path 
    End If 
End Class

用法：

Dim open As New OpenFileDialog 
open.Title = "Add songs" 
open.Filter = "MP3 Files(*.mp3)|*.mp3" 
open.Multiselect = True 
If open.ShowDialog = DialogResult.OK Then 
    For Each SelectedSong As String In open.FileNames 
    Dim songToAdd As New Song 
    songToAdd.Path = SelectedSong 
    songToAdd.Name = GetSafeFileName(SelectedSong.ToString) 
    SongsList.Add(songToAdd) 
    Next 
End If 
Listbox1.DataSource = SongsList.OrderBy(Function(s) s.Name).ToList

来源

2015-09-25 23:27:04 OneFineDay

我试过这个，但没有奏效。下面是代码： ListBox1.Items.Clear（）昏暗排序= SongsList.OrderBy（功能（S）s.SongName）.ToList 昏暗我作为整数对于i = 0到sorted.Count - 1个 ListBox1中.Items.Add（sorted（i）.SongName.ToString） Next –

NullReferenceException –

您在上面写道它是'Name'而不是'SongName'。哪一个？ – OneFineDay

*非常类似OneFineDay的答案...

你并不需要一个自定义类，只需使用一个List(Of FileInfo)：

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click 
    Dim open As New OpenFileDialog 
    open.Title = "Add songs" 
    open.Filter = "MP3 Files(*.mp3)|*.mp3" 
    open.Multiselect = True 
    If open.ShowDialog = DialogResult.OK Then 
     ListBox1.DataSource = Nothing 
     Dim songs As New List(Of FileInfo) 
     For Each SelectedSong As String In open.FileNames 
      songs.Add(New FileInfo(SelectedSong)) 
     Next 
     songs = songs.OrderBy(Function(fi) fi.Name).ToList 
     ListBox1.DataSource = songs 
     ListBox1.DisplayMember = "Name" 
     ListBox1.ValueMember = "FullName" 
    End If 
End Sub 

Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click 
    If ListBox1.SelectedIndex <> -1 Then 
     Dim fi As FileInfo = DirectCast(ListBox1.SelectedItem, FileInfo) 
     Dim name As String = fi.Name 
     Dim fullPath As String = fi.FullName 
     Debug.Print("name = " & name) 
     Debug.Print("fullPath = " & fullPath) 
    End If 
End Sub

来源

2015-09-26 03:34:30

如何排序结构数组？

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