Update Entity Framework object from another object of same type

Question

Is there any method to update an object from a strongly typed object without listing each field ?
Lets consider the following case:

    using (var context = new MyDBEntities())
{
     var user = (User)Session["EditedUser"];
     var oldUser = context.Users.FirstOrDefault(o => o.Id == user.Id);
     oldUser.FirstName= user.FirstName;
     oldUser.LastName = user.LastName;
     etc ....
     context.SaveChanges();
}

I have 29 more fields and I am not willing to write them down one by one every time. What I am looking for should be similar to this

using (var context = new MyDBEntities())
{
     var user = (User)Session["EditedUser"];
     var oldUser = context.Users.FirstOrDefault(o => o.Id == user.Id);
     oldUser=user;
     context.SaveChanges();
}

Which fails for sure because of the entity's primary key violation. What I would like to achieve here is to update all the fields except the primary key value.

Have you tried to attach it? e.g. db.Users.Attach(user); db.Entry(user).State = EntityState.Modified; — Silvermind
– Silvermind, Commented Dec 23, 2013 at 10:28
The user is already in the database, I am trying to update his properties from another user object. Attach will not reference to the old user, It will be attached as a new user. — James Dayeh
– James Dayeh, Commented Dec 23, 2013 at 10:35
AddObject would be a new user, not Attach if you set the [Key] column to the same value of the existing user. — Silvermind
– Silvermind, Commented Dec 23, 2013 at 11:14

Silvermind · Accepted Answer · 2013-12-23 12:21:45Z

4

Used the Attach function thanks to 'Silvermind' Now my code looks like this

using (var context = new MyDBEntities())
{
    try
    {
        var user = (User)Session["EditedUser"];
        context.Users.Attach(user);
        context.ObjectStateManager.ChangeObjectState(user, EntityState.Modified);
        context.SaveChanges();
        Session["EditedUser"] = null;
        return "ok";
    }
    catch (Exception ex)
    {
        return ex.Message;
    }
}

edited Dec 23, 2013 at 12:21

Silvermind

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answered Dec 23, 2013 at 11:51

James Dayeh

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Comments

Anthony Griggs · Accepted Answer · 2020-09-23 18:39:52Z

4

I know the accepted answer is seven year old as of this post, so it is likely done a different way now. I found an alternative method that works from this source. One additional note that I found was that you have to then save the object. Here is a full code example in what worked for me. This turned out to be truly priceless as I have performed many work around methods in updating old/ new objects and this makes it a real one stop shop!

EDIT: Modified to match the much simpler format suggested by Gert Arnold

    [ResponseType(typeof(Order))]
    public IHttpActionResult PutOrder(Order ord)
    {
        if (!ModelState.IsValid)
        {
            return Content(HttpStatusCode.BadRequest, "Could not save order, invalid model.");
        }
        var current = db.Order.Find(ord.OrderId);
        try
        {              
            if (current != null)
            {
                // Update Order in Six Hat to match order in IB
                db.Entry(current).CurrentValues.SetValues(ord);
                db.SaveChanges();
                // TODO: Send Order Change Notifications
            }
        }
        catch(Exception e)
        {
            return Content(HttpStatusCode.BadRequest, e.Message);
        }

        return Ok(current);
    }

edited Sep 23, 2020 at 18:39

answered Sep 22, 2020 at 17:59

Anthony Griggs

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5 Comments

Gert Arnold Over a year ago

Unfortunately, the redundant line db.Entry(current).State = System.Data.Entity.EntityState.Modified; throws away the advantages of CurrentValues.SetValues, which is a leaner update statement. See stackoverflow.com/a/30824229/861716.

Anthony Griggs Over a year ago

@GertArnold Thank you for that... I just basically followed the model that was in the link. Appreciate the much better and simpler format of your method!

Victorio Berra Jan 6 at 22:02

Does this do nested objects, IE navigation properties?

Anthony Griggs Jan 9 at 17:22

@VictorioBerra That is a good question that I must admit that I have not tried yet. However, it makes sense to me that if you can initially save them that way (make sure you have all the includes())... then you should be able to update them that way.

Victorio Berra Jan 11 at 2:31

@anthonygriggs I tested and unfortunately it does not. I'm gonna keep using AutoMapper

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