SQL adding new record on update - sql

Question

I have an MVC5 EF6.1 app that is working the way I want it to in every aspect except editing records.
I am using a view model to handle the create and edit forms. The view model matches the entity model, except it does not include an Id, and it has some extra properties for handling file uploads.
Creating records works perfectly. The edit form populates fields just the way it is supposed to. On update, the changes are recognized.
The problem is that instead of updating the record, a new record reflecting the changes is added to the database. The record that should have been updated is still there.
I have tried everything I can find to try to fix this. I have tried updating with and without EntityState. I have tried setting OriginalValues and CurrentValues. I have even tried using a raw SQL statement. All have the same result: a record with the new data is added, and the original is left unchanged.
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Edit(int id, MyViewModel model)
{
var thisRecord = db.MyEntity.Find(id);
//some stuff to update thisRecord properties
db.SaveChanges();
}
That much works fine. What can I do to change the record I am working on and not make a new one?
Any help would be greatly appreciated. This is driving me nuts.

Answer 1

Try this:
[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Edit(int id, MyViewModel model)
{
var thisRecord = db.MyEntity.Find(id);
thisRecord.SomeProperty = newValue;
// UPDATE: Try adding this line:
_db.Entry(thisRecord).State = EntityState.Modified;
db.SaveChanges();
// Whatever other processing you're doing
}