SplitContainer Panel Resize Issue

Question

The General Problem

The application is C# WinForms .Net 4.0.

I have a SplitContainer that takes up most of the form, it is set to Anchor in all directions so it re-sizes along with the form. The left panel (Panel1) has a simple menu, no problems here. The right panel (Panel2) is more complex and contains a number of nested tab controls (with lots of controls) - it is painfully complex, but it's not changing.

The problem is that re-sizing the form doesn't work so well. In fact, if you resize by dragging the edges slowly then it works ok, but drag quickly or use the "restore" button (top-right of form) then the issue occurs.

---

My Control Hierarchy

The following is a simple example of my control hierarchy, its definitely a cut down version but does highlight the nested tab control which may help with replication:

• Form
  • Split Container (anchor: top, left, bottom, right)
    • SC Panel1 (min width: 300)
      • TreeViewControl (forget what it is called)
    • SC Panel2
      • Panel (anchor: top, left, bottom, right)
        • Tab Control (anchor: top, left, bottom, right)
          • Tab Control w/ lots of pages that overflow screen and require the navigation buttons to show in top right corner (anchor: top, left, bottom, right)

---

Debug Details

After some debugging it appears that it is in fact Panel2 (a child of the split container) that doesn't resize properly, and the actual SplitContainer itself resizes fine.

Here are the debug values that show this...

Full width form, before resize:

splitContainerMain.Width: 1479
splitContainerMain.Panel2.Width: 1206
panelCenter.Width: 1203
tabControlMain.Width: 1215

All as expected, splitContainerMain.Panel2.Width is smaller than splitContainerMain.Width.

After resize where the issue occurs:

splitContainerMain.Width: 815
splitContainerMain.Panel2.Width: 1206
panelCenter.Width: 1203
tabControlMain.Width: 1215

As can be seen, the splitContainerMain.Width has resized as desired, but the splitContainerMain.Panel2.Width and subsequently its children have not.

NOTE: Please remember, the width updates correctly if I manually resize the form slowly - this is not a problem with me not correctly setting any anchors.

---

My Efforts So Far

What I have tried to do is use various Form resize events and try to set the widths manually, but to no avail. I think what I would like to try is to set the Panel2.Width value from within an event of some sort.

---

What I Am Looking For

• Is there anyway to force splitContainerMain.Panel2.Width to resize correctly when the splitContainerMain size changes?
• Alternatively, how can I calculate what the Panel2.Width should be? And how can I set that value from the Form.Resize event? (or another event?)

Answer 1

Though the question is about 6 years old, I opted to answer this because I was in the same situation as the opening post. Unfortunately, the orientation was not specified. So, my answer would address the ones with Horizontal orientation.

Please translate to C# as this code is in VB.

 Private Sub splitContainerMain_Resize(sender As Object, e As EventArgs) Handles splitContainerMain.Resize
    '/* This is a work around about panels being left out when SplitContainer is resized */
    Dim pnl1Height As Single = splitContainerMain.SplitterDistance '/* Get upper panel height */
    Dim pnl2Height As Single = splitContainerMain.Height - splitContainerMain.SplitterDistance '/* Get lower panel height */
    splitContainerMain.Panel1.SetBounds(0, 0, splitContainerMain.Width, pnl1Height) '/* Set Upper panel bounds */
    '/* Set lower panel bounds, with a top of upper panel height plus splitter width */
    splitContainerMain.Panel2.SetBounds(0, pnl1Height + splitContainerMain.SplitterWidth, splitContainerMain.Width, pnl2Height)
End Sub

Answer 2

From what I see u should set anchor to none for controls that are creating problem including splitcontainer pannels.

Also I would suggest to use dock fill property to best use the splitcontainers.

If need further help please provide designer file so can have a better look.

Answer 3

So on each Change event you are creating a new thread, that thread will then wait 100 ms and then do the recize??? thats stupid. You can have a thread created at the constructor, then calling Start() on your thread which could have the following:

private void resizeMe() 
{
    this.BeginInvoke((Action)() => {
        splitContainer.Height = tableBorder.Height;
        splitContainer.Width = tableBorder.Width;
    }
}

Answer 4

Exactly the same problem, below code worked for me:

1. Surround splitContainer in a panel "tableBorder"

On tableBorder

Dock = DockStyle.Fill;

On split Container, (no anchoring)

Dock = DockStyle.None;

2. On tableBorder SizeChanged event

   private void tableBorder_SizeChanged(object sender, EventArgs e)
   {
       new Thread(() => { resizeMe(); }).Start();
   }
   
   private void resizeMe()
   {
       Thread.Sleep(100);
   
       this.BeginInvoke((Action)(() => {
   
           doIt();
   
       }));
   }
   
   private void doIt()
   {
       splitContainer.Height = tableBorder.Height;
       splitContainer.Width = tableBorder.Width;
   }
   

There is a small lag, but works