Question

我有一个简单的（ASP.NET）网页，列出文件夹中特定类型的文件，并在ListView中呈现它们。

我试图通过降序LastWriteTime对它们进行排序，即以反向日期顺序排序。但是，尽管排序过程确实会更改数组的顺序，但它并未对其进行正确排序。例如，一个LastWriteTime为#6/3/2011 12:00:00的项目位于列表顶部，但LastWriteTime为#12/16/2011 12:00:00的另一个项目在排序后位于列表的中间位置。

任何想法为什么？

代码：

        Dim dirInfo As New DirectoryInfo(Server.MapPath(AppSettings.Item("ContentDir")))
        Dim FileArrayList As New ArrayList(dirInfo.GetFiles("*.msg", SearchOption.TopDirectoryOnly))

        Dim SortDirections As New Dictionary(Of String, SqlClient.SortOrder)

        With FileArrayList
            .TrimToSize()
            .Sort(New FileInfoComparer(SqlClient.SortOrder.Descending, "LastWriteTime"))
        End With

FileInforComparer类：

Imports System.IO
Imports System.Reflection


Public Class FileInfoComparer
    Implements IComparer

    Private _sortOrder As System.Data.SqlClient.SortOrder
    Private _sortColumn As String

    ''' <summary>
    ''' Constructs new Comparer object, using the supplied SortOrder and SortColumn parameters
    ''' </summary>
    ''' <param name="sortOrder">Defines the SortOrder for the comparison</param>
    ''' <param name="sortColumn">Defines which column is sorted</param>
    ''' <remarks></remarks>
    Public Sub New(ByVal sortOrder As System.Data.SqlClient.SortOrder, ByVal sortColumn As String)
        _sortOrder = sortOrder
        _sortColumn = sortColumn
    End Sub


    ''' <summary>
    ''' Defines the Sorting mechanism for FileInfo objects
    ''' </summary>
    ''' <param name="x">First FileInfo object to compare</param>
    ''' <param name="y">Second FileInfo object to compare</param>
    ''' <returns></returns>
    ''' <remarks></remarks>
    Public Overridable Overloads Function Compare(ByVal x As Object, ByVal y As Object) As Integer Implements System.Collections.IComparer.Compare

        Dim oX_PI As PropertyInfo = CType(x, FileInfo).GetType.GetProperty(_sortColumn)
        Dim oY_PI As PropertyInfo = CType(y, FileInfo).GetType.GetProperty(_sortColumn)
        Dim Result As Int16 = oX_PI.GetValue(x, Nothing).CompareTo(oY_PI.GetValue(x, Nothing))

        'If DESC then reverse the result
        If _sortOrder = SqlClient.SortOrder.Descending Then Result = Result * -1

        Return Result

    End Function
End Class

Answer 1

LastWriteTime可以作为字符串返回，这解释了排序顺序。值按字符串排序，而不是DateTime对象。将字符串解析为datetime，排序顺序应正确。

Answer 2

这是一个使用LINQ的解决方案。这是用C＃和converted编写的VB，所以希望这有效。

Dim dirInfo = New DirectoryInfo(Server.MapPath(AppSettings.Item("ContentDir")))
Dim fileList = dirInfo.GetFiles("*.msg", SearchOption.TopDirectoryOnly).OrderByDescending(Function(f) f.LastWriteTime)

fileList的类型为IEnumerable<FileInfo>。如果您需要它是一个可变列表，而不是使用ArrayList，我建议使用List<FileInfo>，这可以通过添加.ToList()来结束，就像这样

Dim fileList = dirInfo.GetFiles("*.msg", SearchOption.TopDirectoryOnly).OrderByDescending(Function(f) f.LastWriteTime).ToList()

FileInfoComparer未正确排序（在LastWriteTime上）

2 个答案: