nHibernate Criteria, trying to order by enum name (alphabetical rather than value) - nhibernate

Question

Lets say I have a class that contains a status type, which is defined as an enum like so:
public class MyObject
{
public virtual int Id { get; set; }
public virtual SomeEntity Data { get; set; }
public virtual MyStatusEnum Status { get; set; }
}
public enum MyStatusEnum
{
Active = 1,
Paused = 2,
Completed = 3
}
My mapping done via Fluent nHibernate looks like:
public class MyObjectMap: ClassMap<MyObject>
{
public MyObjectMap()
{
this.Table("my_object_table");
...
this.References(x => x.SomeEntity).Column("some_entity_id").Not.Nullable();
this.Map(x => x.Status).Column("status_type").CustomType<MyStatusEnum>().Not.Nullable();
}
}
Now that the setup is out of the way, my dilemma:
In my repository class, I want to sort all of the MyObject entities by the Status property, which nHibernate persists as an int. However, due to powers beyond my control, I cannot reorder MyStatusEnum so that the enum values are ordered alphabetically. When I create my criteria to select the list of MyObjects, and try to sort it by the Status property, it sorts by the int value of Status.
ICriteria criteria = this.Session.CreateCriteria<MyObject>("obj")
.AddOrder(Order.Asc("Status"))
.List()
I'd really like to be able to order by the enum name. Any ideas would be greatly appreciated.

Answer 1

If you want to sort it in the database, you'd have to sort by a projection with a case statement, but this won't be able to use an index, and might not work depending on your version of NHibernate (there are bugs when sorting by projections that aren't in the select).
Something like this might work:
.AddOrder(Order.Asc(
Projections.SqlProjection(
"CASE {alias}.Status "
+ "WHEN 1 THEN 0 "
+ "WHEN 2 THEN 3 "
+ "WHEN 3 THEN 2 END",
new string[0], new IType[0])))
Another option (better for performance) is to add a property to your class such as StatusOrder which you set equal to the relative position of the current status in your enum and just sort by that field (which you can index).
Yet another option is to define a formula property on your class (ie. specify a formula in the mapping) where the formula specifies a value to sort by depending on the status.

Answer 2

The easy way is to simply refactor your enum so that values and names have the same ordering:
public enum MyStatusEnum
{
Active = 1,
Paused = 3,
Completed = 2
}
But you can always use the List.Sort method to do the job:
enum MyEnum
{
Alpha,
Beta,
Gama
}
static void Main(string[] args)
{
List<MyEnum> list = new List<MyEnum>()
{
MyEnum.Gama,
MyEnum.Beta,
MyEnum.Alpha
};
list.Sort((x, y) => x.ToString().CompareTo(y.ToString()));
}
NHibernate sorts result sets based on how they are stored in the database. From what you said I'm guessing your enums are being stored as integers, hence you won't be able to ask SQL Server to order them by their names because these names are not known by SQL Server.
Unless you store your enums as strings, like discussed in this SO Question, your only option will be to perform the ordering "in memory" and not in the database.