Error when upgrade to silverlight 4

Hi Team,

var results = context.Infos.Where((Infos i) => loadOperation.Entities.Contains(i)).ToList();
results.ForEach((Infos i) => context.Infos.Detach(i)); ​

This my view model code. When i add new item in grid i got below error

"The specified entity is not contained in this EntitySet"

I just install silverlight tools ​5 for Visual studio 2010 and upgrade my project to Silverlight ​5. I also download Rad Controls for Silverlight ​5.

I didn't get this before i upgrade project to S5.

What mistake i did?.

 Pls Help me