Copy a new record with new key from existing record

Question

Have many tables where I have GUID as primary key in each table. I want to create a copy with new Guid from the original record in all tables.

While doing this, I am getting an error The property 'Guid' is part of the object's key information and cannot be modified in line# 9.

1. var project = context.Projects.FirstOrDefault(x => x.Guid == projectGuid);  // existing record
2.           if (project != null)
3.            {
4.            project.Guid = Guid.NewGuid(); // Setting newguid
5.          //....... need same values from rest of the columns
6.
7.            project.CreatedBy = userAccountGuid;
8.            project.CreatedDate = DateTime.Now;
9.            context.Projects.Add(project);   // Adding a new record
10.
11.         }

As @JHBonarius said, you are not creating a copy. You are attempting to modify the already existing project's Guid. — Jose Nuno, Jul 12 '22 at 16:41
Does line not create a new ? If not how can I do it without explicitly copy each column to new object's column. — PowerTech, Jul 12 '22 at 16:46
@JoseNuno I found it. It's twice in the question title and one in the body. It's just missing from the code. — JHBonarius, Jul 12 '22 at 16:47
@PowerTech this is basic C#. Too basic for stack overflow. Just follow the Microsoft or entity framework documentation. — JHBonarius, Jul 12 '22 at 16:48
Does this answer your question? [Entity Framework 5 deep copy/clone of an entity](https://stackoverflow.com/questions/15308747/entity-framework-5-deep-copy-clone-of-an-entity) — Jose Nuno, Jul 12 '22 at 16:59

score 1 · Accepted Answer · answered Jul 13 '22 at 02:58

If you want to clone an entity and that entity's PK is an Identity column, then the easiest way to do that is to detach it, then add it to the DbContext. (rather than Attaching) The DbContext will treat it as a new, untracked entity and assign it a new ID:

var project = context.Projects.AsNoTracking().FirstOrDefault(x => x.Guid == projectGuid);
if (project != null)
    context.Projects.Add(project);

This may look a bit odd, but AsNoTracking() tells the DbContext not to track the entity being loaded. When you add a Project with an Identity column, that column is ignored and a new ID will be assigned. If you aren't using an identity column then you can then just set the project's ID to a new value before adding it to the DbSet.

if (project != null)
{
    project.Id = Guid.NewGuid();
    context.Projects.Add(project);
}

Note that when using GUIDs for PKs/FKs, I would recommend using identity columns using a sequential UUID algorithm such as NewSequentialId() in SQL Server. Even if setting these in code you can find examples of how to generate a suitable endian-sortable variation of the UUID which can save you a lot of performance/storage size pain with indexing.

Copy a new record with new key from existing record

1 Answers1