如何排序結構數組？

-1

我有一個結構數組。它是這樣宣稱的如何排序結構數組？

Public SongsList as New List(Of Song)

「宋」它的結構的名稱。它有2個變量：路徑和名稱; 我想知道如何按名稱排序這個數組。

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

我想這

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

但它拋出一個NullReferenceException。

這是我如何將項目添加到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

來源

2015-09-25 Cosmin Stoian

我編輯了你的q可以在OneFineDay的答案的評論中加入你提到的代碼;但請下一次嘗試包含您嘗試過的代碼 - 即使它不起作用。現在，你能告訴我們如何填寫'SongsList'嗎？ –

爲什麼你在已經是字符串的變量上調用'.ToString'？ – Enigmativity

重複的[什麼是NullReferenceException，我該如何解決它？]（http://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it） –

可以使用Lambda表達式。它使用您在OrderBy函數中選擇的字段。讓我們覆蓋ToString方法來告訴列表框顯示什麼，然後你可以將列表設置爲數據源。

類：

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

來源

2015-09-25 23:27:04 OneFineDay

我試過這個，但沒有奏效。下面是代碼： ListBox1.Items.Clear（）昏暗排序= SongsList.OrderBy（功能（S）s.SongName）.ToList 昏暗我作爲整數對於i = 0到sorted.Count - 1個 ListBox1中.Items.Add（sorted（i）.SongName.ToString） Next –

NullReferenceException –

您在上面寫道它是'Name'而不是'SongName'。哪一個？ – OneFineDay

*非常類似OneFineDay的答案...

你並不需要一個自定義類，只需使用一個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

來源

2015-09-26 03:34:30

如何排序結構數組？

回答

相關問題