vb.net combo box

classy_dog

In a VB.NET 2010 desktop application, I am using the following new logic to load values into a combo box.

Public dirAccessFiles As String() = Directory.GetFiles("H:\FilesTest", "*.accdb")
Try
Dim dir As String

        For Each dir In dirAccessFiles
            cboAccessFile.Items.Add(Path.GetFileNameWithoutExtension(dir))
        Next
    Catch except As Exception
        Console.WriteLine("The process failed: {0}", e.ToString())
    End Try

The user wants the file names to be in descending order in the combo box. Thus, can you tell me how to modify the code list above and/or would you show me code on how I can load file names into the combo box in descending order?

Lost User

That means you need to set the Sorted property to False, and sort the names manually before adding them to the Combo.

Wombaticus

WHat Richard MacCutchan said - but personally I wouldn't bother with any "manual" sorting method / algorithm. Instead, add a listbox, set its Visible property to false, and Sort = True. Then load the items into that and let tt take of sorting them. Then, to get reverse order, just read the items in reverse and load them into your combo box. :)

classy_dog

Would you show me how to write the code you suggested here," Instead, add a listbox, set its Visible property to false, and Sort = True. Then load the items into that and let tt take of sorting them. Then, to get reverse order, just read the items in reverse and load them into your combo box."? Could you give me at least a start on how to set this up?

Wombaticus

Well... Add ListBox1 to form set

ListBox1.Visible = False ' don't want users seeing this
ListBox1.Sorted = True

Public dirAccessFiles As String() = Directory.GetFiles("H:\FilesTest", "*.accdb")

...

For Each dir In dirAccessFiles
ListBox1.Items.Add(Path.GetFileNameWithoutExtension(dir))
Next
' ListBox1 now has the items in alphabetic order
' so, to add them to the combo box in reverse order:
Dim I as integer
For I = ListBox1.Items.Count - 1 To 0 Step -1
cboAccessFile.Items.Add(ListBox1.Items(I))
Next

Sascha Lefevre

What Richard said. Not what Wombaticus said. Sorting is easy. This replaces your posted code except the try-catch-block:

Dim dirAccessFiles As String() = Directory.GetFiles("H:\FilesTest", "*.accdb") _
.Select(Function(x) Path.GetFileNameWithoutExtension(x)) _
.OrderByDescending(Function(x) x) _
.ToArray()

cboAccessFile.Items.AddRange(dirAccessFiles)

(You'll need an "Imports System.Linq" at the top of the file.)

If the brain were so simple we could understand it, we would be so simple we couldn't. — Lyall Watson

Sascha Lefevre

That's a toe-curling suggestion.. please see my answer below ;)

If the brain were so simple we could understand it, we would be so simple we couldn't. — Lyall Watson

Wombaticus

Bah - only to purists! :) Technically, you are quite right of course, but I suspect Linq is a bit beyond our OP at present. Then it depends on one's motivation; there's nothing wrong with "cheating" if getting a working result is what matters. Even if this isn't the best place to use it, this "cheat" is a useful way of sorting items without resorting to complex methods, which our OP could use elsewhere. But without a knowledge of Linq, your answer would be used "by rote" and the OP would learn nothing - other, perhaps, than that maybe he should learn about Linq. I am not really trying to say I'm right and you're not - of course you are; just that there can be a place for the quick (because it doesn't require learning new methods) and dirty solutions sometimes.

Lost User

Yes, that is probably the way I would have done it. However, given the tenor of the question I doubt that the OP could do it without a full sample of code.

Sascha Lefevre

Wombaticus wrote:

but I suspect Linq is a bit beyond our OP at present

You're probably right there but it can also be done without Linq:

Dim dirAccessFiles As String() = Directory.GetFiles("H:\FilesTest", "*.accdb")
Dim list As New List(Of String)()
For Each dir As String In dirAccessFiles
list.Add(Path.GetFileNameWithoutExtension(dir))
Next
list.Sort()
For i As Integer = list.Count - 1 To 0 Step -1
comboBox1.Items.Add(list(i))
Next

If the brain were so simple we could understand it, we would be so simple we couldn't. — Lyall Watson

Wombaticus

This is true - and I have to admit that this obvious solution only occurred to me belatedly. :-O Still, my "trick" has many applications! (I'm not giving up on it that easily! :) )

Sascha Lefevre

Wombaticus wrote:

Still, my "trick" has many applications! (I'm not giving up on it that easily! :) )

:-D I didn't yet have to resort to some such trick - do you have an example where it can't be easily replaced with some non-control-using code?

If the brain were so simple we could understand it, we would be so simple we couldn't. — Lyall Watson

Wombaticus

Well, it could be used in many places in lieu of a sorting algorithm. If what you’re saying is anything that can be read into a ListBox and sorted that way could be read into a List collection, ok fair enough. I guess this old trick goes back before the days of such things... (If they existed in VB3 I wasn’t aware of them!) I don’t really want to labour the point – it is a “dirty” trick, so probably shouldn’t be encouraged, but it’s quick and as easy to implement as a “proper” solution. Otherwise, OK, I give in! </grovels>

Sascha Lefevre

Wombaticus wrote:

I guess this old trick goes back before the days of such things...

Fair enough.. old habits ;)

If the brain were so simple we could understand it, we would be so simple we couldn't. — Lyall Watson

Lost User

It's a very useful tip when creating a TreeView which lists the items in sorted order. You can also add a prefix character to each item so that directories appear before files.

Richard Deeming

You might want to pass StringComparer.OrdinalIgnoreCase to the OrderByDescending function, since file names in Windows aren't case-sensitive. :) If you want to mimic the "natural" sort order that Windows Explorer uses, you'll need a different comparer - for example: Numeric String Sort in C#[^]

"These people looked deep within my soul and assigned me a number based on the order in which I joined." - Homer

Sascha Lefevre

Good suggestion; also the linked article, thank you! :)

If the brain were so simple we could understand it, we would be so simple we couldn't. — Lyall Watson

CHill60

That's a trick I used many times in VB3, 5 and 6 (and some obscure VB derivatives that I'd rather forget about). I agree with the others that there are (arguably) better "dotnetty" ways of doing it, but it's always worth having something like this up your sleeve (especially if you end up supporting any legacy systems) The only thing I would say is that (when possible) I created the listbox dynamically in code only so it was never part of the forms control collection.

classy_dog

Thanks for your helpful answers!

Sascha Lefevre

You're welcome!

If the brain were so simple we could understand it, we would be so simple we couldn't. — Lyall Watson