it can't run

Nov 12, 2012 at 9:54 AM
when i debug the project under VS2010, the Prism.UnityExtensions\UnityBootstrapper.cs throw an exception
Could not load file or assembly 'System.Core, Version=3.5.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' or one of its dependencies. The system cannot find the file specified.

how to solve? Thanks.