Private Function listDir(ByVal CurrentDir As String) As Boolean
        Dim thisdir As New Directoryinfo(CurrentDir)
        TextBox2.Text = ""
        If thisdir.exists Then
            Dim subdirectories As Directoryinfo()
            subdirectories = thisdir.getdirectories
            With thisdir
                TextBox2.Text = "跟路径：" & .Root.tostring() & vbCrLf & _
                "属性 ：" & .Attributes.tostring & vbCrLf & _
                "<目录列表>" & vbCrLf & _
                "文件名".PadRight(28, "-") & "创建文件日期".PadRight(16, "-") & vbCrLf
            End With
            Dim subdir As Directoryinfo
            For Each subdir In subdirectories
                TextBox2.Text &= subdir.name.padright(30) & _
                subdir.creationTime.tostring("d").padleft(20) & vbCrLf
            Next
            Return True
        Else
            Return False
        End If
    End Function
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显示的是Directoryinfo未定义。是怎么回事呀？怎样解决啊？