Question

当我在combobox1中更改选择时，我无法更新combobox2中的内容，我错过了什么或做错了什么？

  Imports System.IO
Public Class Form1

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        'get sub directory\ toolpalette group names...
        ComboBox1.DataSource = New DirectoryInfo("C:\VTS\TREADSTONE LT\ATC").GetDirectories()

        Dim filelocation As String
        filelocation = ("C:\VTS\TREADSTONE LT\ATC\" & ComboBox1.Text & "\")

        'gets file\ paltte names...
        For Each BackupFiles As String In My.Computer.FileSystem.GetFiles(filelocation, FileIO.SearchOption.SearchTopLevelOnly, "*.*")
            ComboBox2.Items.Add(IO.Path.GetFileNameWithoutExtension(BackupFiles))
        Next

        'reloads the combobox contents...
        ComboBox1.Refresh()

    End Sub


End Class

Answer 1

当combobox1选择项更改时，您需要拦截添加适当事件处理程序的事件，然后，在此事件中，使用文件名重新填充第二个组合。

但是，如果使用DirectoryInfo对象列表填充第一个组合，则在检索此对象时，DirectoryInfo不是字符串。您应该提取DirectoryInfo对象并使用FullName属性来查找所需的文件

Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As Object, _
    ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged


    ' First clear the Items collection of the second combo
    ComboBox2.Items.Clear()

    ' Now checks if you have really something selected
    Dim comboBox As comboBox = CType(sender, comboBox)
    if comboBox.SelectedItem Is Nothing Then
        Return
    End If


    Dim di = CType(comboBox.SelectedItem, DirectoryInfo)
    Dim filelocation = di.FullName

    For Each BackupFiles As String In My.Computer.FileSystem.GetFiles(filelocation, FileIO.SearchOption.SearchTopLevelOnly, "*.*")
        ComboBox2.Items.Add(IO.Path.GetFileNameWithoutExtension(BackupFiles))
    Next

End Sub

Answer 2

你的ComboBox1 SelectedIndexChanged事件处理程序应该是这样的..

Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged

  if ComboBox1.SelectedIndex = -1 then exit sub

  Dim filelocation As String
  filelocation = ("C:\VTS\TREADSTONE LT\ATC\" & ComboBox1.Text & "\")

  ComboBox2.Items.Clear() '---> clearing combobox2 list

  'gets file\ paltte names...
  For Each BackupFiles As String In My.Computer.FileSystem.GetFiles(filelocation, FileIO.SearchOption.SearchTopLevelOnly, "*.*")
        ComboBox2.Items.Add(IO.Path.GetFileNameWithoutExtension(BackupFiles))
  Next
End Sub

组合框不更新？ VB.net

2 个答案: