Very Confussed - Variable changing?

[nige]

Hey All,

The following procedures sorts a listview column based on what the tag is, 'Numeric', 'String' or 'Date'. When you click on the column header the sort procedure kicks in. On the first click it will sort ascending and on the second click it will sort descending.

My problem is that when I click a second time it won't sort descending but re-sorts ascending again.

It appears when the sortorder is passed to the ListViewColumnSorter.vb classes it changes back to ascending even though it's called as descending. I've bolded the offending variables using a Numeric search.

Now here's the really iritaing thing, I have exactly the same code in another application and it works perfectly?!?!

    Private Sub lvwResults_ColumnClick(ByVal sender As Object, ByVal e As System.Windows.Forms.ColumnClickEventArgs) Handles lvwResults.ColumnClick
        SortMyListView(Me.lvwResults, e.Column, , True)

        LedgerStyle()
    End Sub

#Region "SortListView"
    Friend Sub SortMyListView(ByVal ListViewToSort As ListView, ByVal ColumnNumber As Integer, Optional ByVal Resort As Boolean = False, Optional ByVal ForceSort As Boolean = False)
        ' Sorts a list view column by string, number, or date.  The three types of sorts must be specified within the listview columns "tag" property unless the ForceSort option is enabled.
        ' ListViewToSort - The listview to sort
        ' ColumnNumber - The column number to sort by
        ' Resort - Resorts a listview in the same direction as the last sort
        ' ForceSort - Forces a sort even if no listview tag data exists and assumes a string sort.  If this is false (default) and no tag is specified the procedure will exit
        Dim SortOrder As SortOrder
        Static LastSortColumn As Integer = -1
        Static LastSortOrder As SortOrder = SortOrder.Ascending
        If Resort = True Then
            SortOrder = LastSortOrder
        Else
            If LastSortColumn = ColumnNumber Then
                If LastSortOrder = SortOrder.Ascending Then
                    SortOrder = SortOrder.Descending
                Else
                    SortOrder = SortOrder.Ascending
                End If
            Else
                SortOrder = SortOrder.Ascending
            End If
        End If

        ' In case a tag wasn't specified check if we should force a string sort
        If String.IsNullOrEmpty(CStr(ListViewToSort.Columns(ColumnNumber).Tag)) Then
            If ForceSort = True Then
                ListViewToSort.Columns(ColumnNumber).Tag = "String"
            Else
                ' don't sort since no tag was specified.
                Exit Sub
            End If
        End If

        Select Case ListViewToSort.Columns(ColumnNumber).Tag.ToString
            Case "Numeric"
                ListViewToSort.ListViewItemSorter = New
 ListViewNumericSort(ColumnNumber, SortOrder)
            Case "Date"
                ListViewToSort.ListViewItemSorter = New ListViewDateSort(ColumnNumber, SortOrder)
            Case "String"
                ListViewToSort.ListViewItemSorter = New ListViewStringSort(ColumnNumber, SortOrder)
        End Select

        LastSortColumn = ColumnNumber
        LastSortOrder = SortOrder
        ListViewToSort.ListViewItemSorter = Nothing
    End Sub
#End Region

ListViewColumnSorter.vb

Imports System.Collections
Imports System.Windows.Forms

Public Class ListViewColumnSorter
    Implements IComparer
    Public Enum SortOrder
        Ascending
        Descending
    End Enum

    Private mSortColumn As Integer
    Private mSortOrder As SortOrder

    Public Sub New(ByVal sortColumn As Integer, ByVal sortOrder As SortOrder)
        mSortColumn = sortColumn
        mSortOrder = sortOrder
    End Sub

    Public Function Compare(ByVal x As Object, ByVal y As Object) As Integer Implements System.Collections.IComparer.Compare
        Dim Result As Integer
        Dim ItemX As ListViewItem
        Dim ItemY As ListViewItem
        ItemX = CType(x, ListViewItem)
        ItemY = CType(y, ListViewItem)
        If mSortColumn = 0 Then
            Result = DateTime.Compare(CType(ItemX.Text, DateTime), CType(ItemY.Text, DateTime))
        Else
            Result = DateTime.Compare(CType(ItemX.SubItems(mSortColumn).Text, DateTime), CType(ItemY.SubItems(mSortColumn).Text, DateTime))
        End If

        If mSortOrder = SortOrder.Descending Then
            Result = -Result
        End If
        Return Result
    End Function
End Class

Public Class ListViewStringSort
    Implements IComparer
    Private mSortColumn As Integer
    Private mSortOrder As SortOrder

    Public Sub New(ByVal sortColumn As Integer, ByVal sortOrder As SortOrder)
        mSortColumn = sortColumn
        mSortOrder = sortOrder
    End Sub

    Public Function Compare(ByVal x As Object, ByVal y As Object) As Integer Implements System.Collections.IComparer.Compare
        Dim Result As Integer
        Dim ItemX As ListViewItem
        Dim ItemY As ListViewItem
        ItemX = CType(x, ListViewItem)
        ItemY = CType(y, ListViewItem)
        If mSortColumn = 0 Then
            Result = ItemX.Text.CompareTo(ItemY.Text)
        Else
            Result = ItemX.SubItems(mSortColumn).Text.CompareTo(ItemY.SubItems(mSortColumn).Text)
        End If
        If mSortOrder = SortOrder.Descending Then
            Result = -Result
        End If
        Return Result
    End Function
End Class

Public Class ListViewNumericSort
    Implements IComparer
    Private mSortColumn As Integer
    Private mSortOrder As SortOrder

    Public Sub New(ByVal sortColumn As 
Integer, ByVal sortOrder As SortOrder) '<------This is when it changes
        mSortColumn = sortColumn
        mSortOrder = sortOrder
    End Sub

    Public Function Compare(ByVal x As Object, ByVal y As Object) As Integer Implements System.Collections.IComparer.Compare
        Dim Result As Integer
        Dim ItemX As ListViewItem
        Dim ItemY As ListViewItem
        ItemX = CType(x, ListViewItem)
        ItemY = CType(y, ListViewItem)
        If mSortColumn = 0 Then
            Result = Decimal.Compare(CType(ItemX.Text, Decimal), CType(ItemY.Text, Decimal))
        Else
            Result = Decimal.Compare(CType(ItemX.SubItems(mSortColumn).Text, Decimal), CType(ItemY.SubItems(mSortColumn).Text, Decimal))
        End If
        If mSortOrder = SortOrder.Descending Then
            Result = -Result
        End If
        Return Result
    End Function
End Class

Public Class ListViewDateSort
    Implements IComparer
    Private mSortColumn As Integer
    Private mSortOrder As SortOrder

    Public Sub New(ByVal sortColumn As Integer, ByVal sortOrder As SortOrder)
        mSortColumn = sortColumn
        mSortOrder = sortOrder
    End Sub

    Public Function Compare(ByVal x As Object, ByVal y As Object) As Integer Implements System.Collections.IComparer.Compare
        Dim Result As Integer
        Dim ItemX As ListViewItem
        Dim ItemY As ListViewItem
        ItemX = CType(x, ListViewItem)
        ItemY = CType(y, ListViewItem)
        If mSortColumn = 0 Then
            Result = DateTime.Compare(CType(ItemX.Text, DateTime), CType(ItemY.Text, DateTime))
        Else
            Result = DateTime.Compare(CType(ItemX.SubItems(mSortColumn).Text, DateTime), CType(ItemY.SubItems(mSortColumn).Text, DateTime))
        End If
        If mSortOrder = SortOrder.Descending Then
            Result = -Result
        End If
        Return Result
    End Function
End Class

[Shaggy Hiker]

That code is seriously annoying to read on my screen as I can't get that main snippet to fit within the screen, so I can't scroll in both directions at any one time. Still, put a breakpoint on this line:

If Resort = True Then

And step forwards from there. I don't use static variables, but it sure looks to me like you always change the sort order to Ascending every time you enter the sub, which means that it wouldn't flip flop the way you expect it to.

[nige]

Hey Shaggy...

I've put a carriage return on the offending lines so you should see the bolded text. The second bolded section of code is where the sortorder = 'Descending' but when it steps to the third section of code (at the bolded sortorder) it becomes Ascending.

As I said above, the code works perfectly in another program I have.

I just can't understand what's going on?

[stanav]

I think the problem is that you have 4 different SortOrder enums... But I'm not 100% sure though. What I'd do is to consolidate all 4 column sorter classes into a single 1, and change the contructor to accept 1 more parameter which indicates the data type of the column being sorted. In the Compare function, you do a select case on the data type and do the compare accordingly.

[nige]

I think the problem is that you have 4 different SortOrder enums... But I'm not 100% sure though. What I'd do is to consolidate all 4 column sorter classes into a single 1, and change the contructor to accept 1 more parameter which indicates the data type of the column being sorted. In the Compare function, you do a select case on the data type and do the compare accordingly.

Hey Stanav,

I've remarked out all the other classes except the numeric one and re ran the code. Unfortunately the same problem occurs?

N

[nige]

I've also started up a completely new application added a listview used the exact same code and it works perfectly?

[nige]

Ok I've now got it working. I copied the Class to my main .vb file and exlcuded the ListViewColumnSorter.vb from the project.

It now works?????

Very strange indeed, can anyone explain?