Many of us prefer to disable the designer when editing XAML, mostly for performance reasons. If you experience a big delay when opening and even making changes to XAML files, you might want to disable the designer. Of course if you use the designer, this fix is not for you.
To disable the designer, make sure there are no XAML files open on VS 2010:
1 – Right click on a XAML file on solution explorer
2 – Select “Open with…” from context menu
3 – Select “Source Code (Text) Editor”
4 – Click on “Set as Default” button