无法在实体上设置字段/属性

Question

I have been on a project with entity framework in DDD pattern. I don't use the default custom tool for the entity and I have a repository and some model classes.

I have 3 tables in my entity framework:

1. Category
2. CategoryContent
3. Content

Category with categoryContent and content with categoryContent have 1 to many relationship. (I don't use many to many here because I have some properties in CategoryContent table)

When I send a request for the list of CategoryContent and show content.Title of this list in MVC I have seen this error:

Unable to set field/property CategoryContents on entity type System.Data.Entity.DynamicProxies.Content_731FEFC3E064D6098DC133918117C2359E2F308D2EB1E5D8D986538641AAB7CD.

But when I traced, the program doesn't have any problems and returned data and show.

I use the message system (request and response message in the service project).

this code is a method for return list of contentcategory .

 public IEnumerable<CategoryContent> GetContents(int categoryID)
    {
        Query query = new Query();
        OrderByClause order = new OrderByClause();
        order.PropertyName = "ID";
        order.Desc = true;
        query.OrderByProperty = order;
        query.Add(new Criterion("CategoryID", categoryID, CriteriaOperator.Equal));

        return  categoryContentRepository.FindBy(query);
    }

categoryContentRepository is an object from CategoryContentRepository class in Repository project for management work with DB.

in MVC Controllers:

public ActionResult Content(int id)
    {
        var contentService = ServiceFactory.CreatContentService();
        var response = contentService.GetContents(id).ToList();

        return PartialView("_Content", response);
    }

in view (_content.cshtml):

@model List<Plus.Model.CategoryContent>

@foreach (var item in Model)
{
    @Html.ActionLink(item.Content.Title, "Amir")
}

Model Classes:

public class Category: ValidationBase, IAggregateRoot
{
    public int ID { get; set; }

    [NotNullOrEmpty()]
    public string Name { get; set; }

    [NotNullOrEmpty()]
    public int Ordering { get; set; }

    public int? ParentID { get; set; }
public Guid ModifiedBy { get; set; }
public DateTime ModifiedOn { get; set; }
public string ModifiedReason { get; set; }
public bool Deleted { get; set; }
public bool Active { get; set; }

    
    public virtual Category Parent { get; set; }
    public virtual IList<Category> Childeren { get; set; }
    public virtual IList<CategoryContent> CategoryContents { get; set; }
}

public class CategoryContent : ModelBase, IAggregateRoot
{
    public int ID { get; set; }
    public int ContentID { get; set; }
    public int CategoryID { get; set; }

    public virtual Content Content { get; set; }
    public virtual Category Category { get; set; }
}

public class Content: ModelBase, IAggregateRoot
{
    public int ID { get; set; }
    public string Title { get; set; }
    public string Intro { get; set; }
    public int? ParentID { get; set; }
    public bool IsSeries { get; set; }
    public byte LikeVoteStatus { get; set; }

    public virtual IList<SubContent> SubContents { get; set; }
    public virtual Content Parent { get; set; }
    public virtual IList<Content> Childeren { get; set; }
    public virtual CategoryContent CategoryContents { get; set; }
}

Answer 1

Code of content model has a bug:

public virtual CategoryContent CategoryContents { get; set; }

and right code is:

public virtual IList<CategoryContent> CategoryContents { get; set; }