• Download SimpleCollapsiblePanel - 73.07 KB

Introduction

One of my last projects requiered a large amount of info to be displayed into cathegories. Due the unbalanced population of each group, the Tab control wa not an option. So, I turned to collapsible Panels and GroupBoxes so the user could hide or show the information he needed.

There are many and wonderful collapsible controls in Codeproject, buy I needed something very simple and, most important, the poasibility of nesteing the "collapsers". The ones I tested had extrange interactions both with the FlowLayoutPanel and the AutoSize feature.

I had no time to develope a custom control, and nearly by chance I came with this simple solution.

Using the code

Two elements were needed: a GroupBox (or a Panel) and collapsing/expanding Button. The solution is simple, but what happens if you need a dozen or more collapsers. Copy and paste is not elegant and can lead to tedious debugging.

Can a "universal collapsing button" be made? Yes. Here it is.

Private Sub chkbCollapser_CheckedChanged(ByVal sender As System.Object,
    _ByVal e As System.EventArgs) Handles chkbCollapser.CheckedChanged
 
    If Not Me.Created Then Exit Sub
    
    Dim ctrl As Control = CType(sender, Control).Parent
    Dim chk As CheckBox = CType(sender, CheckBox)

    If chk.Checked Then
        ctrl.AutoSize = True
        chk.Text = "-"
    Else
        ctrl.AutoSize = False
        ctrl.Height = 18
        chk.Text = "+"
    End If
End Sub 

Only three points of interest in the code

• The Me.Created test to avoid code execution when loading the form.
• The ctrl reference to the button's parent (both Panel or GruopBox work fine). This means that the button must obviously be inside the Panel or Group. I use to place it at upper right corner and change the Anchor property from the default Top,Left value to Top,Right.
• The chk reference to the button itself. This allows to place the same code into as many buttons as needed. It's time to say that I don't use a Button, but a CheckBox with Button Appearance.

You only need to copy the code to the first collapsing button you need. Then just Copy' Paste it as required. The Sub headear automatically will be added with the Handle elements for the copies.

Private Sub chkbCollapser_CheckedChanged(ByVal sender As System.Object, 
	_ByVal e As System.EventArgs) _
		Handles chkbCollapser.CheckedChanged, CheckBox1.CheckedChanged, _
			CheckBox5.CheckedChanged, CheckBox4.CheckedChanged, _
			CheckBox3.CheckedChanged, CheckBox2.CheckedChanged, _
			CheckBox8.CheckedChanged, CheckBox9.CheckedChanged, _
			CheckBox13.CheckedChanged, CheckBox12.CheckedChanged, _
			CheckBox11.CheckedChanged, CheckBox10.CheckedChanged

The Sample project allows to see how I manage with FlowLayoutPanels together with my Collapsible Panel/GroupBox