In Win forms there was support for Microsoft’s Multiple Document Interface applications which allow you to open multiple windows in the same workspace.

This UI feature wasn’t carried over to the original WPF standard as it was felt that this design standard wasn’t something that was needed with Microsoft’s new interfacing standards and it was more of an upgrade not to have it..

However a lot of enterprise users really missed the MDI windows of the original windows applications so the quest to re-invent MDI was back on. Many folks have had differing implementations.. One of the latest is called Chronos and it has some really cool features..

It can be found on Codeplex.com..

http://chronoswpf.codeplex.com/

This latest release (Beta 2) features

• Added cached composition on windows & widgets for Render Tier 0/1 machines(this should help to improve window & widget dragging performance).
• Added a simple widget configuration system.
• Metro theme design time fixes & improvements 
• Restyled login window with a zune-like style.
• Shell window header changes to bring it to front when the mouse is over it
• Bug fixes.

Check it out today..