错误：

<m:innererror>
<m:message>
The 'ObjectContent`1' type Failed to serialize the response body for content type 'application/json; charset=utf-8'.
</m:message>
<m:type>System.InvalidOperationException</m:type>
<m:stacktrace/>
<m:internalexception>
<m:message>
No NavigationLink factory was found for the navigation property 'Languages' from entity type 'MvcWebRole1.Models.User' on entity set 'Users'. Try calling HasNavigationPropertyLink on the EntitySetConfiguration.
 Parameter name: navigationProperty
</m:message>
<m:type>System.ArgumentException</m:type>
<m:stacktrace>
at System.Web.Http.OData.Builder.EntitySetLinkBuilderAnnotation.BuildNavigationLink(EntityInstanceContext instanceContext,IEdmNavigationProperty navigationProperty,ODataMetadataLevel MetadataLevel)
 at System.Web.Http.OData.Formatter.Serialization.ODataEntityTypeSerializer.WriteNavigationLinks(EntityInstanceContext context,ODataWriter writer,ODataSerializerContext writeContext)
 at System.Web.Http.OData.Formatter.Serialization.ODataEntityTypeSerializer.WriteEntry(Object graph,IEnumerable`1 propertyBag,ODataSerializerContext writeContext)
 at System.Web.Http.OData.Formatter.Serialization.ODataEntityTypeSerializer.WriteObjectInline(Object graph,ODataSerializerContext writeContext)
 at System.Web.Http.OData.Formatter.Serialization.ODataFeedSerializer.WriteFeed(Object graph,ODataSerializerContext writeContext)
 at System.Web.Http.OData.Formatter.Serialization.ODataFeedSerializer.WriteObjectInline(Object graph,ODataSerializerContext writeContext)
 at System.Web.Http.OData.Formatter.Serialization.ODataFeedSerializer.WriteObject(Object graph,ODataMessageWriter messageWriter,ODataSerializerContext writeContext)
 at System.Web.Http.OData.Formatter.ODataMediaTypeFormatter.<>c__DisplayClassa.<WriteToStreamAsync>b__9()
 at System.Threading.Tasks.TaskHelpers.RunSynchronously(Action action,CancellationToken token)
</m:stacktrace>
</m:internalexception>
</m:innererror>

我的用户看起来像这样：

public class User
{
    [Key]
    public int UserId { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string UserName { get; set; }

    public string Password { get; set; }
    public virtual ICollection<Language> Languages { get; set; }

    public User()
    {
        Languages = new List<Language>();
    }
}

而我的UsersController for OData看起来像这样：

public class UsersController : EntitySetController<User,int>
{
    WorldChatContext db = new WorldChatContext();

    public override IQueryable<User> Get()
    {
        return db.Users.AsQueryable();
    }

    protected override User GetEntityByKey(int key)
    {
        return db.Users.FirstOrDefault(p => p.UserId == key);
    }

    public override HttpResponseMessage Post(User entity)
    {
        db.Users.Add(entity);
        db.SaveChanges();
        return base.Post(entity);
    }
}

我正在呼叫我在路由中设置的以下url：http://127.0.0.1:81/odata/如果我在我的用户模型中注释了导航属性,则可以使用它.

我究竟做错了什么？我已经尝试将[Serializable,KnownType(typeof(Language))]放在我的用户类之上,但由于某种原因我不能使用KnownType.我如何使我的OData与此导航属性一起使用？