Q:

What am I missing out? (An entity with the same identity already exists in this EntitySet.)

I am using DTOs and converters in an entity framwork scenario. I want to update an entity. So I put this statement:
databasecontext.Tablename(s).Attach(entityobj);
Whenever it gets here the program ends with this error:
An entity with the same identity already exists in this EntitySet.
I felt I could get around this by saying  databasecontext.Tablename(s).Detach(entityobj);
before I called Attach again. But the program still fails on the Attach statement.
What am I missing? Which method on the DB context calls Update in the Domain Service?

A:

It looks like you are keeping the context open while you make the changes.
In that case you do not need to reattach the object to the context.
If you open a context, get an object from a context, then close the context, make some changes to the object, then open a new context. In this case you need to attach the object to the context.

