ListView: How to sort numbers?

[AlvaroF1]

The following code is working fine, but when it's storing numbers...

Friend Class Form1
    Inherits System.Windows.Forms.Form
    Private Sub ListView1_ColumnClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.ColumnClickEventArgs) Handles ListView1.ColumnClick
        If e.Column <> sortColumn Then
            sortColumn = e.Column
            ListView1.Sorting = SortOrder.Ascending
        Else
            If ListView1.Sorting = SortOrder.Ascending Then
                ListView1.Sorting = SortOrder.Descending
            Else
                ListView1.Sorting = SortOrder.Ascending
            End If
        End If
        ListView1.Sort()
        ListView1.ListViewItemSorter = New Comparer(e.Column, ListView1.Sorting)
    End Sub
End Class
Friend Class Comparer
    Implements IComparer
    Private Col As Integer
    Private Order As SortOrder
    Public Sub New()
        Col = 0
        Order = SortOrder.Ascending
    End Sub
    Public Sub New(ByVal column As Integer, ByVal order As SortOrder)
        Col = column
        Me.Order = order
    End Sub
    Public Function Compare(ByVal x As Object, ByVal 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)
        If Order = SortOrder.Descending Then returnVal *= -1
        Return returnVal
    End Function
End Class

For example it returns:

1
10
2
20

Instead of:

1
2
10
20


How to fix it?

Thanks.

[parminder]

it treats as text


use numbers as

01
02
.
.
09
10
.
.
20

[AlvaroF1]

[PT Exorcist]

that is what u can call like a kind of bug..in alfabetic order its 1,10,2,20 and in numeric order 1,2,10,20 but as the listview works with text order then ur screwed. u'll have to recode a lot if u want to put it the right way

[trisuglow]

But the code is doing what you asked it to! Your Compare function is doing a string comparison.

Use this Compare function instead to sort the list in numerical order.

Function Compare(ByVal x As Object, ByVal y As Object) As Integer _
                                Implements System.Collections.IComparer.Compare
            Dim item1 As ListViewItem = CType(x, ListViewItem)
            Dim item2 As ListViewItem = CType(y, ListViewItem)
 
            Return Math.Sign(CLng(Val(item1.SubItems(mIndex).Text)) _
                                    - CLng(Val(item2.SubItems(mIndex).Text)))
        End Function

If your list has mixed columns (some numeric and others text) then you will need to write two Comparer classes and use the appropriate one for each column.

[AlvaroF1]

Originally posted by trisuglow
If your list has mixed columns (some numeric and others text) then you will need to write two Comparer classes and use the appropriate one for each column.

Interesting.

Do you know how to detect if it's number or text and then use the correct comparer?

Thanks again.

[trisuglow]

Here's an extract from my code. I assume you know what data-type is stored in each column?

Private Sub lvwShoppingList_ColumnClick(ByVal sender As Object, _
                    ByVal e As System.Windows.Forms.ColumnClickEventArgs) _
                                        Handles lvwShoppingList.ColumnClick
 
        Select Case e.Column
 
            Case 0, 1 'Product code, Description
                lvwShoppingList.ListViewItemSorter = _
                                                New CompareByString(e.Column)
 
            Case 2 'Loop A quantity
                lvwShoppingList.ListViewItemSorter = _
                                            New CompareByQuantity(MXLoopA)
 
            Case 3 'Loop B quantity
                lvwShoppingList.ListViewItemSorter = _
                                            New CompareByQuantity(MXLoopB)
 
            Case 4 'Loop C quantity
                lvwShoppingList.ListViewItemSorter = _
                                            New CompareByQuantity(MXLoopC)
 
            Case 5 'Loop D quantity
                lvwShoppingList.ListViewItemSorter = _
                                            New CompareByQuantity(MXLoopD)
 
            Case 6 'Total quantity
                lvwShoppingList.ListViewItemSorter = New CompareByQuantity(0)
 
 
        End Select
 
    End Sub

[AlvaroF1]

Good one, but if don't we know it?

[trisuglow]

The items stored in each column (the subitems of your listviewitems) are data type Object. So, you can't really talk about them being text or numbers. It's up to you to decide how you want to sort them. I guess the only way to find out is to first loop through your list and do an IsNumeric() check on each item in the column to find out if they are all numbers.

Does that help, or have I missed the point?

[AlvaroF1]

That helped!

Thanx.