NHibernate doesn't save one property only

Question

I'm trying to update a single column in the table. No UPDATE issued whatsoever (checked using SQL Profiler). No errors.

• Class mapping has dynamic-update="true".
• No versioning enabled on the class.
• Flush mode Commit.
• Property mapped without any insert/update modifiers (<property name="Deleted" />).
• Property is auto-implemented (public virtual bool Deleted { get;set;}).

• NH 3.3.0, .NET 4, x64.

  using (var transaction = this._session.BeginTransaction())
  {
      try
      {
          var order = this.session.Load<Order>(id);
          order.Deleted = true;
          this._session.Update(order);
          transaction.Commit();
      }
      catch (Exception)
      {
          transaction.Rollback();
          throw;
      }
  }
  

Answer 1

Based on the comments, what you are trying to do is create a proxy without getting the current state from the DB (using session.Load), then issue a dynamic update.

This will not work. NHibernate does not record individual changes to properties; instead, it:

• Compares the current state of tracked entities against a snapshot of the property values that were retrieved from the database.
• Based on that, determines which entities are dirty (i.e. have changes)
• It generates the SQL update statement. If using dynamic-update, it will only contain the modified properties.

If you use session.Load, as soon as you access the Deleted property, NH will load the record from the database. Whether you use session.Load or session.Get, session.Update on an already tracked entity is a no-op.

Alternatively, if you already have the state for all the order properties, you can update without loading:

var order = GetTheOrderFromMemory();
order.Deleted = true;
session.Update(order);
transaction.Commit();

This will not respect dynamic-update, as NH doesn't have a snapshot to compare with...

...which is why HQL is the only way to do a one-shot update of an individual property.