Trouble Sorting ListView

Question

All,

I have a ListView w/filename, data, time and size fields. I've copied the code from this article http://msdn.microsoft.com/en-us/library/ms996467.aspx to use in my solution. Problem is, when I click a column header the first time, it sorts, but when I click the same header a second time, to sort in reverse, the column stays in the same order as it was just sorted in. Any suggestions? Thanks in advance.

Answer 1

try this:

http://www.vbforums.com/showpost.php?p=3499291&postcount=8

Answer 2

The article you link to starts out with code that only sorts in one direction and then shows how to update the code to be able to switch directions.  Did you implement the second version of the code?  If so can you post your code for the ListView.ColumnClick event and the ListViewItemComparer class? 

Here is the code from the article:

Private Sub listView1_ColumnClick(sender As Object, e As
                System.Windows.Forms.ColumnClickEventArgs)
    ' Determine whether the column is the same as the last column clicked.
    If e.Column <> sortColumn Then
        ' Set the sort column to the new column.
        sortColumn = e.Column
        ' Set the sort order to ascending by default.
        listView1.Sorting = SortOrder.Ascending
    Else
        ' Determine what the last sort order was and change it.
        If listView1.Sorting = SortOrder.Ascending Then
            listView1.Sorting = SortOrder.Descending
        Else
            listView1.Sorting = SortOrder.Ascending
        End If
    End If 
    ' Call the sort method to manually sort.
    listView1.Sort()
    ' Set the ListViewItemSorter property to a new ListViewItemComparer
    ' object.
    listView1.ListViewItemSorter = New ListViewItemComparer(e.Column, _
                                                     listView1.Sorting)
End Sub

Class ListViewItemComparer
    Implements IComparer 
    Private col As Integer
    Private order as SortOrder
    
    Public Sub New()
        col = 0
        order = SortOrder.Ascending
    End Sub
    
    Public Sub New(column As Integer, order as SortOrder)
        col = column
        Me.order = order
    End Sub
    
    Public Function Compare(x As Object, y As Object) As Integer _
                        Implements System.Collections.IComparer.Compare
        Dim returnVal as Integer = -1
        returnVal = [String].Compare(CType(x, _
                        ListViewItem).SubItems(col).Text, _
                        CType(y, ListViewItem).SubItems(col).Text)
        ' Determine whether the sort order is descending.
        If order = SortOrder.Descending Then
            ' Invert the value returned by String.Compare.
            returnVal *= -1
        End If

        Return returnVal
    End Function
End Class

Answer 3

Blackwood,

Here's my slightly modified code- I'm pretty sure I only changed names to suit my tastes. When I get into the office tomorrow, I'll double-check my code against that of the article and I'll also try bibliophage's link.

Private Sub FileList_ColumnClick(ByVal sender As Object, ByVal e As System.Windows.Forms.ColumnClickEventArgs) Handles FileList.ColumnClick
   Me.FileList_ColumnClick
   With FileList
      If e.Column <> SortColumn Then
         SortColumn = e.Column
         .Sorting = SortOrder.Ascending
      Else
         If .Sorting = SortOrder.Ascending Then
            .Sorting = SortOrder.Descending
         ElseIf .Sorting = SortOrder.Descending Then
            .Sorting = SortOrder.Ascending
         End If
      End If



      .ListViewItemSorter = New ListViewItemComparer(e.Column, .Sorting)
      .Sort()
   End With 'FileList
End Sub 'FileList_ColumnClick

Class ListViewItemComparer
   Implements IComparer

   Private m_ColumnNumber As Integer
   Private m_SortOrder As SortOrder

   Public Sub New()
      m_ColumnNumber = 0
      m_SortOrder = SortOrder.Ascending
   End Sub

   Public Sub New(ByVal column_number As Integer, ByVal sort_order As SortOrder)
      m_ColumnNumber = column_number
      m_SortOrder = sort_order
   End Sub

   ' Compare the items in the appropriate column for objects x and y.
   Public Function Compare(ByVal x As Object, ByVal y As Object) As Integer _
          Implements System.Collections.IComparer.Compare

      Dim item_x As ListViewItem = DirectCast(x, ListViewItem)
      Dim item_y As ListViewItem = DirectCast(y, ListViewItem)

      ' Get the sub-item values.
      Dim string_x As String
      If item_x.SubItems.Count <= m_ColumnNumber Then
         string_x = String.Empty
      Else
         string_x = item_x.SubItems(m_ColumnNumber).Text.Trim()
      End If

      Dim string_y As String = String.Empty
      If item_y.SubItems.Count <= m_ColumnNumber Then
         string_y = String.Empty
      Else
         string_y = item_y.SubItems(m_ColumnNumber).Text.Trim()
      End If

      ' Compare them.
      If m_SortOrder = SortOrder.Ascending Then
         If IsNumeric(string_x) And IsNumeric(string_y) Then
            Return Val(string_x).CompareTo(Val(string_y))
         ElseIf IsDate(string_x) And IsDate(string_y) Then
            Return DateTime.Parse(string_x).CompareTo(DateTime.Parse(string_y))
            'Else
            '   Return DateTime.Parse(string_x).CompareTo(DateTime.Parse(string_y))
            'End If
         Else
            Return String.Compare(string_x, string_y, True)
         End If
      Else
         If IsNumeric(string_x) And IsNumeric(string_y) Then
            Return Val(string_y).CompareTo(Val(string_x))
         ElseIf IsDate(string_x) And IsDate(string_y) Then
            Return DateTime.Parse(string_y).CompareTo(DateTime.Parse(string_x))
            'Else
            '  Return DateTime.Parse(string_y).CompareTo(DateTime.Parse(string_x))
            'End If
         Else
            Return String.Compare(string_y, string_x, True)
         End If
      End If
   End Function
End Class

Greg

Answer 4

Code looks fine. Did you step through the code to see if the conditions are executing as expected.

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