MahApps/MahApps.Metro — pull request #716 by Amrykid (2013-10-19 19:00:05+00:00)
Title: Passive Grouping+Virtualization in ComboBox

Added ComboBoxHelper that has an extension method that enables virtualization and grouping in .NET 4.5 and will do nothing in .NET 4.0.

Fixes #596