Entity Framework 4: Update Single Record

Question

I've got a Method that has a Model "Address" as a parameter.

Now inside this method I want to "overwrite" my existing Address in the Database with the provided address - just like updating it in SQL.

I do the inserting-bit like this:

            Context.Addresses.AddObject(adr);
            Context.SaveChanges();

How do I do the updating-part?

I've tried something like this:

   public void Update(Address adr)
   {
            Context.Addresses.Attach(adr);
            Context.SaveChanges();
   }

Sadly, this does not work... I've also tried plenty of other codes, but none of them worked.

So how can I update an existing record in my DB when I get an object of the modified record as a parameter?

Thank you

Easiest would be to retrieve the existing address, then use ModelCopier or AutoMapper to update it with the new values, then call SaveChanges(). — mxmissile
– mxmissile, Commented Jan 26, 2012 at 22:54
possible duplicate of how to update an entity in Entity Framework 4 .NET — Ladislav Mrnka
– Ladislav Mrnka, Commented Jan 27, 2012 at 9:14

Eranga · Accepted Answer · 2012-01-27 07:42:23Z

2

You need to tell EF that the entity is updated by calling ApplyCurrentValues

 public void Update(Address adr)
 {
        Context.Addresses.ApplyCurrentValues(adr);

        Context.SaveChanges();
 }

edited Jan 27, 2012 at 7:42

answered Jan 27, 2012 at 0:02

Eranga

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4 Comments

SeToY Over a year ago

This does not work. I can't remember the exact exception, but it says something like "ObjectManager can't manage more than one object with the same KeyField" or something like that.

Eranga Over a year ago

@SeToY Then use ApplyCurrentValues method as shown in updated answer

SeToY Over a year ago

This results in: "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." When I first call context.Attach(adr), no exception occurs but it doesn't update the row in the db

Eranga Over a year ago

@SeToY Check whether an istance with same PK is tracked by the context. If so use ApplyCurrentValues. Otherwise Attach the new instance and set its state as Modified.

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