How do I sort controls on a FlowLayoutPanel

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Hello folks:

I have a flow layout panel where users can add buttons. However, while my buttons place themselves nicely on the panel, they are not sorted by name. Here is how the user adds the button:

Private Sub btnAddCategory_Click(sender As Object, e As EventArgs) Handles btnAddCategory.Click

        Dim newButton As New Button

        With newButton

            .Size = CType(New Point(211, 34), Drawing.Size)
            .FlatStyle = Windows.Forms.FlatStyle.Flat
            .FlatAppearance.BorderSize = 0
            .FlatAppearance.BorderColor = System.Drawing.Color.Gray
            .BackColor = System.Drawing.Color.Gray

            .Name = "btn" & TextBox3.Text
            .Text = TextBox3.Text

        End With

        pnlCategories.Controls.Add(newButton)
    


    End Sub

But my buttons are not sorted. So I thought of doing the following to sort my buttons:

Private Sub pnlCategories_ControlAdded(sender As Object, e As ControlEventArgs) Handles pnlCategories.ControlAdded

        For Each btn As Button In Me.Controls.OfType(Of Button)() _
                               .OrderBy(Function(b) b.Text)

        Next

    End Sub

But nothing happens, I know is possible to sort the buttons, but I can't seem to get it to work.

Posted 3-Apr-14 7:26am

qbndl8

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Maciej Los · Answer 1 · 2014-04-03T09:14:00

As far as i know, when controls are added to FlowLayoutPanel, they are "sorted" in the order of addition.

I'd suggest to use List<T>[^] generic class to manage controls. It contains several properties and methods which enables you to sort elements, add, check if exists, clear, etc.

Implementation:
1) Before you add control to FlowLayoutPanel,
a) check if it exists in the collection,
b) if not exists - add it to List<T>
c) sort elements
2) Remove controls from FlowLayoutPanel
3) Add controls to FlowLayoutPanel from List<T>

Maybe it's not elegant solution, but at this moment i have no better idea.

Sergey Alexandrovich Kryukov · Answer 2 · 2014-04-03T09:22:00

Solution 2

This is because you are not doing anything to sort the children. The method OrderBy does no have any side effects. It returns a collection of reordered object. You need to do one more step: remove all controls from its parent and populate them again, this time, in the order you got in the object returned as the result of the ordering.

Besides, the use of OfType is questionable. It's clear what to do if all the children are buttons, but in this case, you should use all the controls, not just buttons. If some of the control are not buttons, you can use some other sorting criteria.

To populate controls, use the property System.Windows.Forms.Control.Controls and the method System.Windows.Forms.Control.ControlCollection.Add:
http://msdn.microsoft.com/en-us/library/system.windows.forms.control.controls%28v=vs.110%29.aspx[^],
http://msdn.microsoft.com/en-us/library/system.windows.forms.control.controlcollection.add(v=vs.110).aspx[^],
http://msdn.microsoft.com/en-us/library/system.windows.forms.control.controlcollection.addrange%28v=vs.110%29.aspx[^].

—SA

Posted 3-Apr-14 9:22am

Sergey Alexandrovich Kryukov

Comments

Maciej Los 3-Apr-14 15:33pm

Ok, your proposal says almost the same what i said. But i understand your intentions.

Sergey Alexandrovich Kryukov 3-Apr-14 15:38pm

Yes, but the difference is: you suggest to add one more collection. I simply say that this collection is not needed.
—SA

Maciej Los 3-Apr-14 15:43pm

Wait a moment. I don't get it. Are you saying that Form.FlowLayoutPanel.Controls is the collection which OP needs to manage? I'm bit tired today and my brain is going crazy ;)

Sergey Alexandrovich Kryukov 3-Apr-14 15:48pm

If you read my answer slower, you'll get it. I don't know what do you mean by "manage". No.
OP calls "OrderBy" in LINQ. This LINQ returns some collection of ordered controls. This is just the calculation, without any side effect. But the collection needed for population already exists. OP does not do anything to the panel itself.
—SA

Maciej Los 3-Apr-14 16:00pm

My "manage" means your "populate" ;) Manage => add, sort, delete controls from FlowLayoutPanel. I agree, Linq does not do affects on control's position on the Panel (i hope it is correctly spelled and you can understand what i mean). That's why i suggest to use List<t> generic class.

Sergey Alexandrovich Kryukov 3-Apr-14 16:38pm

Fair enough. So, you can populate from the collection returned from the LINQ. No need to create one more collection.
I did not mean the collection Control.Controls. Apparently, it is always used (but not by OP, so far :-). Yes, as I say, OP failed to affect order in this collection.
—SA

Maciej Los 3-Apr-14 16:51pm

Got it!
+5!

Sergey Alexandrovich Kryukov 3-Apr-14 16:53pm

Aha! :-)
Thank you.
—SA