Question

I am new to NHibernate. We are using Dapper for retrieval and planning to use NHibernate for CRUD.

I am trying to remove the child object through parent list object in one to many relationship.

This works when I retrieve the object using NHibernate session and remove the item.

var mercedes = Read("chevrolet"); //queries from nhibernate session
var model = mercedes.Models.Where(c => c.Id == 181).Single(); 
mercedes.Models.Remove(model);

When I manually create the object and attach thecars models, it is unable to remove it.

var mercedes = new Make() { Id = 77, Name = "chevrolet" };//manually created the object
mercedes.Models = GetAllModels(77);//I have it in-memory            
var model = mercedes.Models.Where(c => c.Id == 173).Single();
mercedes.Models.Remove(model);

I think I am doing something weird. But I am able to add/update the models using second approach, so why can’t i remove it. Any insights please.

Answer 1

When you create a new domain object it isn’t attached to the NHibernate session (unless you are creating a new object and call Save, for instance). As such, deleting from the models collection doesn’t actually do anything.

Your second example doesn’t seem like a particularly good practice but you can recreate an object and attach it to your NHibernate session using Session.Lock (Merge or Update are fairly normal depending on your preferred behavior).