DarkDockPanel add DarkDocument NullReferenceException within DarkControl

[merthsoft]

I have a DarkDockPanel, and within it there is a split control. When I try to add an additional DarkDockPanel to the split control panel, I get the following exception:

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Microsoft Visual Studio
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Failed to create component 'DarkDockPanel'.  The error message follows:

 'System.NullReferenceException: Object reference not set to an instance of an object.

   at DarkUI.Docking.DarkDockRegion.OnCreateControl()

   at System.Windows.Forms.Control.CreateControl(Boolean fIgnoreVisible)

   at System.Windows.Forms.Control.CreateControl(Boolean fIgnoreVisible)

   at System.Windows.Forms.Control.CreateControl()

   at System.Windows.Forms.Control.ControlCollection.Add(Control value)

   at System.Windows.Forms.Design.ParentControlDesigner.AddChildControl(Control newChild)

   at System.Windows.Forms.Design.ParentControlDesigner.AddControl(Control newChild, IDictionary defaultValues)

   at System.Windows.Forms.Design.ControlDesigner.InitializeNewComponent(IDictionary defaultValues)

   at System.Drawing.Design.ToolboxItem.CreateComponentsCore(IDesignerHost host, IDictionary defaultValues)

   at System.Drawing.Design.ToolboxItem.CreateComponents(IDesignerHost host, IDictionary defaultValues)

   at Microsoft.VisualStudio.Design.Toolbox.AutoToolboxManagerService.ToolboxManagerTool...'
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OK   
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It appears you cannot add a DarkDockPanel to a DarkControl.

[merthsoft]

Note I was able to get past this by manually creating the objects and adding to the splitcontainer panel controls.

[RobinPerris]

DarkDockPanel is not meant to be nested. You should only ever have one. It is the parent control which contains all the regions, panels, drag areas, etc.

You can follow a step-by-step on how to configure it here:
https://github.com/RobinPerris/DarkUI/wiki/Tabbed-document-interface

If that doesn't help solve the problem you face, can you explain what you're trying to achieve with your current control hierarchy? I might be able to come up with a solution that works with DarkUI.

[merthsoft]

Basically the structure I have is this
MainForm is a DarkForm
MainForm has a DarkDockPanel called mainPanel
mainPanel gets a DarkDocument I created called UserAdminControl
UserAdminControl has a SplitContainer in it.
SplitContainer.Panel2 has a DarkDockPanel called dock
dock gets a DarkDocument I created called RoleAssignmentControl

When I try to drag-and-drop the DarkDockPanel onto the SplitContainer.Panel2 from the designer I get the error message above. However, if I do it grammatically there are no errors:

var dock = new DarkDockPanel
{
    Dock = DockStyle.Fill
};

splitContainer1.Panel2.Controls.Clear();
splitContainer1.Panel2.Controls.Add(dock);

var roleControl = new RoleAssignmentControl();
dock.AddContent(roleControl);

So ultimately I'm able to work around this, just not from the designer.