Retargeting solution from .Net 4.0 to 4.5 - how to retarget the NuGet packages?

Question

I have migrated a solution that is currently targeting .NET 4.0 in VS2010 to VS2012 and now I would like to re-target it to .Net 4.5

What I am not sure about is the

Answer 1

After trying the accepted answer unsuccessfully I would like to suggest a less risky command:

Update-Package  -ProjectName  -Reinstall -IgnoreDependencies

For more info: http://blog.nuget.org/20121231/a-quick-tutorial-on-update-package-command.html