更新唯一的非主键

Question

In my DB, I have a column defined as a Unique index. I generated my EF model from the DB (I don't know how this uniqueness was translated to the model. How do I check this?).
When I try to update this field in a record using

entity.Users.ApplyCurrentValues(user);

I get the following error:

An object with a key that matches the key of the supplied object could not be found in the ObjectStateManager. Verify that the key values of the supplied object match the key values of the object to which changes must be applied.

How can I update a unique (non-primary!) field?

Answer 1

We'd have to see some more code to determine where you're obtaining user object from to get a clearer picture of what's going on.

I believe ApplyCurrentValues is used to update changes that have been made to an object that already exists in the ObjectContext ; if you didn't initially obtain your user instance from your context, you'll get the error above (the error is telling you it's unable to find the object you're trying to update).

MSDN : Copies the scalar values from the supplied object into the object in the ObjectContext that has the same key.

You may well be able to Attach() your user if it's a detached object, or you may be able to load your user from this context and then use ApplyCurrentValues with the retrieved object.