WCF with Entity Framework Code First relationship - wcf

Question

I'm learning WCF, and tried to make a small service that exposes a Project and its tasks (the standard Entity Framework hello world).
The class structure is the following:
public class Project
{
public int ProjectId { get; set; }
public string Name { get; set; }
public string Description { get; set; }
public DateTime CreationDate { get; set; }
public virtual ICollection<Task> Tasks { get; set; }
}
public class Task
{
public int TaskId { get; set; }
public string Title { get; set; }
public virtual Project RelatedProject { get; set; }
}
The DB context comes after:
public class ProjectContext : DbContext
{
public DbSet<Project> Projects { get; set; }
public DbSet<Task> Tasks { get; set; }
}
Finally, the service endpoint:
public IEnumerable<Project> getProjects()
{
ProjectContext p = new ProjectContext();
return p.Projects.AsEnumerable();
}
The problem is that this model will throw a System.ServiceModel.CommunicationException, but, If I remove the virtual properties from the model, It would work, but I would loose the entity framework links between Project and Task.
Anyone with a similar setup?

Answer 1

I banged my head against the wall several hours with this one. After extensive debugging, google gave the answer and I feel right to post it here since this was the first result I got in google.
Add this class on top of your [ServiceContract] interface declaration (typically IProjectService.cs
public class ApplyDataContractResolverAttribute : Attribute, IOperationBehavior
{
public void AddBindingParameters(OperationDescription description, BindingParameterCollection parameters)
{
}
public void ApplyClientBehavior(OperationDescription description, System.ServiceModel.Dispatcher.ClientOperation proxy)
{
var dataContractSerializerOperationBehavior =
description.Behaviors.Find<DataContractSerializerOperationBehavior>();
dataContractSerializerOperationBehavior.DataContractResolver =
new ProxyDataContractResolver();
}
public void ApplyDispatchBehavior(OperationDescription description, System.ServiceModel.Dispatcher.DispatchOperation dispatch)
{
var dataContractSerializerOperationBehavior =
description.Behaviors.Find<DataContractSerializerOperationBehavior>();
dataContractSerializerOperationBehavior.DataContractResolver =
new ProxyDataContractResolver();
}
public void Validate(OperationDescription description)
{
// Do validation.
}
}
Requirements are
using System.ServiceModel.Description;
using System.Data.Objects;
using System.ServiceModel.Channels;
Then under the [OperationContract] keyword add [ApplyDataContractResolver] keyword and you are set!
Big thanks to http://blog.rsuter.com/?p=286

Answer 2

For sending data trough WCF you should disable lazy loading (dataContext.ContextOptions.LazyLoadingEnabled = false;).
To be sure the data you want is loaded you need to use eager loading ( trough the Include method).
You need to change your function to:
public IEnumerable<Project> getProjects()
{
ProjectContext p = new ProjectContext();
p.ContextOptions.LazyLoadingEnabled = false;
return p.Projects.Include("Tasks").AsEnumerable();
}