Return self referencing model in JSON format using Web Api 2 controller - json

Question

I have a self referencing model called Folder and also an Entity called Content which contains the Folder Entity.
public class Folder : BaseEntity
{
public int Id { get; set; }
public string Name { get; set; }
public int? ParentId { get; set; }
public virtual Folder Parent { get; set; }
public virtual ICollection<Folder> Children { get; set; }
}
public class Content : BaseEntity
{
[Key]
public int Id { get; set; }
public string Title { get; set; }
public string HTML { get; set; }
public string Summary { get; set; }
public int XmlConfigId { get; set; }
public int FolderId { get; set; }
public virtual Folder Folder { get; set; }
}
Here is my Application Db context
public class ApplicationDbContext: DbContext
{
public DbSet<Folder> Folders { get; set; }
public DbSet<Content> Contents { get; set; }
public ApplicationDbContext() : base("ProjectDB") {
Database.SetInitializer<ApplicationDbContext>(null);
}
}
Everything works fine if i am using a razor view to display the data and also i am able to access the The Folder property that is inside the Content Entity.
The problem is when i try to display the data using Web API.
My web API
public class ContentApiController : ApiController
{
[HttpGet]
public IEnumerable<Content> GetAllContents()
{
return _unitofwork.Contents.GetAllContents();
}
}
On the Web API, the GetAllContents() function just returns the Entity models coming directly from the Folders DBSet. It is not calling the ToList() function since i want to do lazy loading. Here is the code for the GetAllContents() function.
public IEnumerable<Content> GetAllContents()
{
return ApplicationDbContext.Contents.Include(c=>c.Folder);
}
So in order for this to work i have to add.
Configuration.LazyLoadingEnabled = false;
to my applicationDbContext constructor which i really don't want.
and also
Global.asax
GlobalConfiguration.Configuration.Formatters.Remove(GlobalConfiguration.Configuration.Formatters.XmlFormatter);
WebApiConfig
JsonMediaTypeFormatter jsonFormatter = config.Formatters.OfType<JsonMediaTypeFormatter>().Single();
jsonFormatter.UseDataContractJsonSerializer = false;
jsonFormatter.SerializerSettings.Formatting = Newtonsoft.Json.Formatting.Indented;
jsonFormatter.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;
jsonFormatter.SerializerSettings.PreserveReferencesHandling = Newtonsoft.Json.PreserveReferencesHandling.None;
Is there any way to expose the json data without out turning off Lazy loading. Thanks.

Answer 1

Just call ToList on your query, or, even better, ToListAsync:
[HttpGet]
public async Task<IEnumerable<Content>> GetAllContents()
{
return await _unitofwork.Contents.GetAllContents().ToListAsync;
}
Even if you enable LazyLoading, you cannot avoid to materialize your data before returning it to the client (and let the Serializer do its work).
In your MVC example, the framework itself enumerates the result in your View (I suppose), and thus you are not directly calling ToList, but in your scenario you have to materialize your Entities explicitly.
Please note that there is no performance issue in calling ToList/ToListAsync in your controller.