Projecting from a model with an integer property to class with Enum property

Question

I have my model classes set up with the integer properties just as they are stored in the database. So a sample model might look like:

public class TaskModel
{
    public int TaskId { get; set; }
    public int TaskStatus { get; set; }
}

But on my actual business classes I want to use enums, so the matching business class would look like:

public class Task
{
    public int TaskId { get; set; }
    public Status TaskStatus { get; set; }
}

I then want to use Automapper's LINQ projection features to query these business classes, like:

 return db.Tasks.Where( t => t.TaskStatus == 1 ).Project().To<Task>();

But when I do this I get this error:

Unable to create a map expression from System.Int32 to MyNamespace.TaskStatus

I've been able to resolve it by setting up the mapping as such:

Mapper.CreateMap<TaskModel, Task>()
   .ForMember(t => t.TaskStatus, opt => opt.MapFrom(m => (TaskStatus)m.TaskStatus))
   .ReverseMap();

This seems to work (so far), but my question is there a better or DRYer way to do this. The problem is I will need to do this for a ton of properties across a ton of models and classes. Seems like there should be a simpler way to do what is essentially a simple cast with having to write 100's of lines of mapping code.

Answer 1

You can do this with a type converter:

Mapper.CreateMap<int, TaskStatus>()
    .ProjectUsing(src => (TaskStatus)src);

This will be used everywhere. The reason you have to do this is because some LINQ providers have different ways of dealing with enum conversions and persistence, so you have to use the right expression it expects (and AutoMapper doesn't assume it knows what EF or NHibernate or whatever need).