Question

我有一个结构数组。它被宣布为这样

Public SongsList as New List(Of Song)

＆＃34;宋＆＃34;它的结构名称。它有2个变量：路径和名称; 我想知道如何按名称对这个数组进行排序。

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

我试过这个

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

但它会抛出一个NullReferenceException。

这就是我向SongsList添加项目的方式

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

Answer 1

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

班级：

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

Answer 2

*非常类似于OneFineDay的答案......

您不需要自定义类，只需使用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

如何对结构数组进行排序？

2 个答案: