Readonly Strategies with Nhibernate and Fluent Nhibernate

Question

I been reading nhibernate for beginners 3.0 and been reading about common mistakes(a few of them I been making)

I am wondering what are some strategies for making one or more records readonly. Right now I get all the rows back and loop through them making them readonly through session.Readonly().

I like in the book that they do with fluent

class EntityMap : ClassMap<Entity>
{
    public EntityMap()
    {
        SchemaAction.None();
        ReadOnly();

        // Mappings
    }
 }

What I am not sure is what happens if I need these records to not be Readonly? To me this means I have to make this exact same mapping minus those 2 lines of code.

So I would like to do this and have ReadonlyEntityMap and EntityMap but I rather not have to duplicate all the settings twice.

Anyone have ideas on how do to this? Or better ideas for readonly?

Mark Perry Mark Perry · Accepted Answer · 2011-09-14T22:42:12

Using ReadOnly() on your mapping will disable any updates back to the database when you modify the properties of the object.

If you want to apply some sort of ReadOnly and Writeable strategy I would suggest using a Fluent Convention and a marker interface or similar.

You can also apply ReadOnly() to a property if you want to disable writes on just that one property. I use that technique to avoid writing back to Computed Columns in SQL Server.

Something like this:

public interface IReadOnly{} //Mark entities with this interface

public class ReadOnlyConvention
     : IClassConvention, IClassConventionAcceptance<IClassInspector>
{
  public void Accept(IAcceptanceCriteria<IClassInspector> criteria)
  {
    criteria.Expect(x => x.EntityType Is IReadOnly);
  }

  public void Apply(IClassInstance instance)
  {
    instance.ReadOnly();
  }
}

Update: If you want to do you time conversion thing I would suggest creating an IUserType for your DateTime object which does the conversion to the user time without modifying the underlying data.

Readonly Strategies with Nhibernate and Fluent Nhibernate

2 Answers