ServiceStack: Update<T>(...) produces 'duplicate entry' - servicestack

Question

I have tried reading the docs, but I don't get why the Update method produces a "Duplicate entry" MySQL error.
The docs says
In its most simple form, updating any model without any filters will update every field, except the Id which is used to filter the update to this specific record:
So I try it, and pass in an object, like below. A row with id 2 already exists.
using (var _db = _dbFactory.Open())
{
Customer coreObject = new Customer(...);
coreObject.Id = 2;
coreObject.ObjectName = "a changed value";
_db.Update<Customer>(coreObject); // <-- error "duplicate entry"
}
Yes, there are options using .Save and such, but what am I missing with the .Update? As I read it, it should use its Id property to update the row in the db, not insert a new row?

Answer 1

The issue with this method is that you're updating a generic object T but your Update API says to update the Concrete Customer type:
public void MyTestMethod<T>(T coreObject) where T : CoreObject
{
long id = 0;
using (var _db = _dbFactory.Open())
{
id = _db.Insert<T>(coreObject, selectIdentity: true);
if (DateTime.Now.Ticks == 0)
{
coreObject.Id = (uint)id;
_db.Delete(coreObject);
}
if (DateTime.Now.Ticks == 0)
{
_db.DeleteById<Customer>(id);
}
if (DateTime.Now.Ticks == 0)
{
coreObject.Id = (uint)id;
coreObject.ObjectName = "a changed value";
_db.Update<Customer>(coreObject);
}
}
}
Which OrmLite assumes that you're using a different/anonymous object to update the customer table, similar to:
db.Update<Customer>(new { Id = id, ObjectName = "a changed value", ... });
Which as it doesn't have a WHERE filter will attempt to update all rows with the same primary key.
What you instead want is to update the same entity, either passing in the Generic Type T or have it inferred by not passing in any type, e.g:
_db.Update<T>(coreObject);
_db.Update(coreObject);
Which will use OrmLite's behavior of updating entity by updating each field except for Primary Keys which it instead used in the WHERE expression to limit the update to only update that entity.
New Behavior in v5.1.1
To prevent accidental misuse like this I've added an Update API overload in this commit which will use the Primary Key as a filter when using an anonymous object to update an entity, so your previous usage:
_db.Update<Customer>(coreObject);
Will add the Primary Key to the WHERE filter instead of including it in the SET list. This change is available from v5.1.1 that's now available on MyGet.