Alphabetical sorting in VB seems to be different in listboxes and in Access

[HONOREDANCESTOR]

I've found that when I compare the following 2 characters in VB dot
net:
"_" and "A"
VB says that "A" is less than "_".
But when I used a sorted listbox in VB dot net, the reverse is true.
Also, when I sort a column in a Microsoft Access database, the reverse
is true.
I need a consistent sorting method.
Is the VB sort order changeable?
Thanks,
HA

 

[rowe_newsgroups]

I've found that when I compare the following 2 characters in VB dot
net:
"_" and "A"
VB says that "A" is less than "_".
But when I used a sorted listbox in VB dot net, the reverse is true.
Also, when I sort a column in a Microsoft Access database, the reverse
is true.
I need a consistent sorting method.
Is the VB sort order changeable?
Thanks,
HA

Generally when you when you want a custom sort you create an IComparer
object to do the comparing. To do this with a listbox you have a few
options.

1) Manually sort the items
2) Use an object such as a List(Of T) or an Array that accepts an
IComparer object in an overloaded Sort method
3) Inherit a ListBox and create your custom Sort routine

Out of personal preference I would chose option number 3. I consider
it much cleaner than using outside code.

Here's a complete demo project that should demonstrate how to
implement the overrides and an IComparer object to sort the list in
descending alphabetical order. Just create a new Windows Application
and paste this as the code behind for Form1:

///////////////////////
Public Class Form1

Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As
System.EventArgs) Handles MyBase.Load
Dim lb As New MyListBox()
lb.Items.Add("a")
lb.Items.Add("c")
lb.Items.Add("b")
lb.Items.Add("e")
lb.Items.Add("d")

Me.Controls.Add(lb)

lb.Sorted = True
End Sub

End Class

Public Class MyListBox
Inherits ListBox

Public Shadows Property Sorted() As Boolean
Get
Return _Sorted
End Get
Set(ByVal value As Boolean)
MyBase.Sorted = False
_Sorted = value
If value Then Sort()
End Set
End Property
Private _Sorted As Boolean = False

Protected Overrides Sub Sort()
Dim items As New List(Of String)(Me.Items.Count)

For Each item As String In Me.Items
items.Add(item)
Next

items.Sort(New SortComparer())

Me.Items.Clear()

For Each item As String In items
Me.Items.Add(item)
Next
End Sub

Protected Class SortComparer
Implements IComparer(Of String)

Public Function Compare(ByVal x As String, ByVal y As String)
As Integer Implements System.Collections.Generic.IComparer(Of
String).Compare
Return StringComparer.CurrentCultureIgnoreCase.Compare(y,
x)
End Function

End Class

End Class
///////////////////////

Unfortunately, that doesn't show you how to make an "A" less than a
"_", so you'll have to add in that bit of logic into the Compare
method.

Good Luck!

Thanks,

Seth Rowe

 

[Patrice]

It's likely you are doing a culture insensitive comparison all along with
culture sensitive comparisons. Keep in mind that the sort order can vary for
each culture (or if you don't take at all the culture into account).

For details try :
http://msdn2.microsoft.com/en-us/library/a7zyyk0c(VS.80).aspx and around
(Comparing and Sorting Data for a Specific Culture)

 

[Patrice]

IMO it could be the other way round (i.e. Access and the listbox would be
correct for its current culture but the OP does IMO a culture insensitive
comparison in his code).

In this case he would just have to perform culture sensitive comparison in
his code to match its culture and the UI/Access behavior (link provided in a
earlier response).

Hopefully the OP will clarify which is the correct sort order (_ before A
seems quite natural at least here in France)...

 

[Jack Jackson]

This has caused me great grief.

There are two main kinds of string comparisons in .NET, culture
sensitive and those based on the binary values of the characters. Some
comparisons use the former and some use the latter. In the US English
culture the default ComparisonOption makes most non-alphanumberic
characters (single quote, dash, etc) be essentially ignored when
sorting.

Bound objects use the default culture sensitive sort. The comparison
operators (> < ) use an ordinal sort.

If you want your code to match the bound item sort, use String.Compare
and supply the appropriate ComparisonType. I have been unable to find
a way to change the sorting that is done by binding objects when you
don't control the data types of the items being sorted, such as row
items in a DataTable.