why 'EasingDoubleKeyFrame' does not exist in XML namespace 'http://schemas.microsoft.com/winfx/2006/xaml/presentation'.

if you get this error that means you are trying to use a WPF4 feature in 3.5

easyway out is to change it to change it to SplineDoubleKeyFrame

how to solve The attachable property 'VisualStateGroups' was not found in type 'VisualStateManager'. exception in VS2008

No need to move to VS2010 to solve this problem,

just have to install these two patches to get the VisualStateGroups in XAML view

http://code.msdn.microsoft.com/KB958017/Release/ProjectReleases.aspx?ReleaseId=1719
http://code.msdn.microsoft.com/KB958017/Release/ProjectReleases.aspx?ReleaseId=1719

then it works like a magic.