How do I create new entities based on old entities in Entity Framework?

Question

I need to

1. load some entities into memory,

2. change a couple of its 'scalar'

3. property values -without touching its Navigation Properties. and

4. SAVE them as a NEW Entity into the Db.

   How can I achieve this in EntityFramework, is it enough to set the object's ID to NULL to save it as a new entity or what should be the trick?

Answer 1

You simply need to change the entity state from Modified to Added and Entity Framework will perform an insert instead of an update.

Example using DbContext API:

DbContext context = // ...
foreach (var entityEntry in context.ChangeTracker.Entries())
{
    if (entityEntry.State == EntityState.Modified)
         entityEntry.State = EntityState.Added;
}
ct.SaveChanges();