update object created in another datacontext

I need your help very much. I'd like to update object created in another datacontext; Here is my code. Insert statement works well but I can't write code for update

var dataContext = new ReconNewDataContext();           
        if (Id == 0)
        {
            var item = this;
            dataContext.RequestIO.InsertOnSubmit(item);
            dataContext.SubmitChanges();
            Id = item.Id;
        }
        else
        {
            var item = this;
            //update object
        }        

I've read Linq2SQL: Update object not cre开发者_Python百科ated in datacontext

I've tried to use .Attach(this) .Attach(this,true) .Attach(this, oldObjectFromBase) but always I've an errors.

I know I can get object from database and manually transfer data from modified object, but there will be new fields. It means that I must always append these new fields in Save() method.

Is there any "beautiful" method to update object created in another datacontext?

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Check out this article: http://omaralzabir.com/linq_to_sql__how_to_attach_object_to_a_different_data_context/

Also, in your example, for update, try doing:

var item = new ObjectBeingUpdated();
//copy over properties from old object to new object, make sure pk's match

//Attach this new object

Something similar worked for my coworker I believe.

UPDATE: Check this out for more info about attach: http://blogs.msdn.com/b/dinesh.kulkarni/archive/2007/10/08/attach-if-you-have-something-detached.aspx

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You could use the following pattern:

1. Fetch existing object from repository
2. Use AutoMapper to copy properties
3. Save your object back.