Entity Framework: “Store update, insert, or delete statement affected an unexpected number of rows (0).” [closed]

Answer 1

I got this exception when attaching an object that didn't exist in the database. I had assumed the object was loaded from a separate context, but if it was the user's first time visiting the site, the object was created from scratch. We have auto-incrementing primary keys, so I could replace

context.Users.Attach(orderer);

with

if (orderer.Id > 0) {
    context.Users.Attach(orderer);
}