Thank you for the additional details, Alex.
What you have observed (background color inheritance) is a WinForms feature. The change of the background color is caused by the change of the base class of the user control - you modify it from
UserControl to
DockPanel. But
DockPanel has its own default background color which is different than the
Control color.
In order to avoid the background inheritance set the
BackgroundColor property of the user control to
"Control" color. Please, do that from the designer of the user control, not from the designer of the Form where the user control is added.
After that when you drag-and-drop new controls inside the user control they will be with their default background colors instead of the background color of
DockPanel.
It is possible that there is serialized code for
BackgroundColor for the already added controls in the user control so remove that code before setting
BackgroundColor for the user control.
The observed behavior of
RadPanelBar and
RadListBox is the default one - you can confirm it by using Microsoft buttons inside the user control. If the user control inherits
DockPanel the button will be with dark gray background just like RadPanelBar and the RadListBoxes inside it.
This behavior should be the same for the older version as well. Let me know if this information helps.
Kind regards,
Angel
the Telerik team