Detailed description in forum thread: http://www.telerik.com/community/forums/winforms/dock/closing-last-window-with-middle-clicking-the-document-tab-throws-an-exception.aspx

I am using nested dock objects. I find that if I close one tabbed window using the X icon, the control closes properly, leaving the other tabbed windows opened. However, if I try to close the tabbed window using the keyboard sequence Ctrl+F4, this also closes one of the tabs within another window!
I have attached an example form. This contains a RadDock with 2 windows, DocumentWindow1 and DocumentWindow2. DocumentWindow1 also contains two document windows, DocumentWindow3 and DocumentWindow4. The sequence of events to reproduce this behaviour is as follows:
- In designer mode: set focus on DocumentWindow2 and Save
- Run app
- Form opens with focus set on DocumentWindow2, as expected
- Set focus on DocumentWindow1
- Set focus back to DocumentWindow2
- Press Ctrl+F4 to close DocumentWindow2
- This closes DocumentWindow2 but also closes DocumentWindow4 within DocumentWindow1.
Please note that if I use the X button to close DocumentWindow2, only DocumentWindow2 gets closed, as expected.

I've discovered a behavioral issue with the tool-window when one of its containing control's data-binding is updated.

I'm designing an application using the MVVM design pattern with a basic View and View-Model. The View is a form that contains a RadDock, ToolWindow containing a Label, and a Button to update the Label's Text; and data-binding setup to the ToolWindow's property "DockState" and a Label's property "Text". The View-Model contains the bound properties "ToolWindow1DockState" and "Label1Text", which implements INotifyPropertyChanged to update the respective controls; and a method used to update Label1's text.

After I click "Auto-hide" on ToolWindow1 and click the "Change Text" button, I'm expecting ToolWindow1 to remain in the Auto-hide state. Instead, ToolWindow1 is placed in the Docked state.

1) Start with new Forms application.

2) Add RadDock set to Fill to the Form.

3) Open Designer.

4) Add ToolWindows docked Top and Right.  Add two ToolWindows docked fill.

5) Close Designer.

6) Open Designer.

7) Delete two docked ToolWindows.

8) Close Designer.

9) Deleted ToolWindows remain.  I also had them become tabbed with the 
ToolWindow docked to the Top in a previous test.

10) In the Designer, if I check the box, the two ToolWindows become docked
Left.  If I close the Designer and re-open it, I can then delete them.

11) I deleted all ToolWindows in the Designer and closed it.

12) The ToolWindows are removed.

13) Upon re-opening the Designer and adding windows, they do not appear
upon closing the Designer.

14) It appears that the documentContainer is missing from the DocumentOutline.
However, it is still present in the code because if I delete the RadDock, and
then re-add it, the name of the new documentContainer is numbered higher than
the first one.  If I try to rename it from 1 to 3, it tells me that 1 is still
in use.

15) Adding ToolWindows at this point works again.

IMPROVE: RadDock - currently when middle click is executed the ActiveWIndows closes instead of the clicked one

Steps to reproduce:
1. Add a new form to a project and set MdiContainer to true
2. Drag a RadDock onto the form and set the AutoDetectMdiChildren to true
3. Add another form to be used as MdiChild
4. Drag a button onto the second form and in the Click event handler add call to this.Close()
5. Run the project and add an MdiChild form to the MdiContainer form.
6. Press the button on the child form. You will see an exception.

1. Create a new project containing RadDock
2. Add two buttons, the first one will add a document window, the second one will remove it.
3. Run the project and add and remove document windows multiple times.

FIX. RadDock - arranging DocumentWindows tabs in design time is not possible.

ADD. RadDock - functionality to change the text orientation of the AutoHideTab
Comment: The text of AutoHideTab can be flipped for achieving of these requirements as the following code snippet demonstrates:
private void radDock1_TransactionCommitted(object sender, RadDockTransactionEventArgs e)
{
if (e.Transaction is AutoHideTransaction)
{
foreach (DockWindow window in e.Transaction.AssociatedWindows)
{
window.AutoHideTab.FlipText = true;
window.AutoHideTab.TextAlignment = ContentAlignment.MiddleCenter;
}
}
}

The ShowAutoHidePopup method should enable showing auto hidden pop-ups.

In addition, if this ContextMenu is called from a control contained in an autohide DockWindow that is currently expanded, this window becomes collapsed.

There is a memory leak in RadDock when closing a document window with the context menu.

Add functionality in the Advanced Layout Designer to delete ToolWindows

In very specific cases, if one resizes RadDock, its content is not resized/redrawn correctly.

When saving the layout RadDock saves the windows as they appear in the DockWindows collection. However, improvement to save the current toolwindows position will be great addition.

FIX. RadDock does not load the ActiveWindow correctly.

FIX. RadDock SplitterWidth property is not taken into consideration, nor setting the MinSize of each splitter individually.

changes
---------------------------------
event is changed to ItemSelecting - tabstrip now is pageview (documentTabStrip1.TabStripElement.ItemSelecting += new EventHandler<Telerik.WinControls.UI.RadPageViewItemSelectingEventArgs>(TabStripElement_ItemSelecting))
introduce new powefull events for RadDock - SelectedTabChanging / SelectedTabChanged


Create a dock with couple of documents.
Subscribe to the TabSelecting event of RadTabStripElement and cancel it showing a message box indicating the cancellation.
The message box will be shown 5 times.

Create a new project and add RadForm
Add RadDock and set its Dock property to Fill
Run the project and start resizing the form, you will see that the memory increases