使用NHibernate插入或保存时为Object Proxies提供什么值

Question

Let us assume that we have Class TableChild and Class TableParent. They correspond to similar tables in the database. TableChild and TableParent have a relationship as indicated by their names. TableChild class has a property of type TableParent to replicate the relationship in our classes. Now when I am inserting a new object for TableChild, how do we provide the value for the property of TableParent. Should we just assign the ID of TableParent to the TestChild. Or do we fetch the whole object from the DB using the ID value of TableParent and then assign this object to the TableChild. The second method is feasible but would bring more performance overhead as we have to issue extra Select statements.

The mapping that we are using is the simple Please do suggest some easy methods, if possible, to store the relationship to the child table while inserting new values for the same.

Answer 1

In C#, the relationships are object references.

public class TableParent
{
}

public class TableChild
{
    TableParent Parent { get; set; }
}

To create a child with a known parent, give it a parent object that is known to NHibernate. Using ISession.Load() gives a proxy object without touching the database (assuming lazy loading has not been disabled).

// create and save a child with a known parent
var c = new TableChild {
    Parent = session.Load<TableParent>( parent_id );
};
session.Save( c );