EF Update in Context existing Entities

there is a entity e1 in dbContext1, already loaded from database and its sent by server over WCF, changed byclient, sent back over WCF to server, its' not the same entity e1, its another object e2.
If you say Save to Context nothing is saved.
dbContext1 is the Ef Cache and should always contain the newest state of all objects


1) create a new context, attach the e2 and save it to database, update the dbContext 1 from database
2) update e1 with values (and references9 from e2, save to database with DbContext1
3) Detach e1 (set State to Detached)  and Attach e2, set e2. EnitytState to modified