在 Silverlight 域服务中包含子实体集合

Question

我有一个域服务类，如下所示

[MetadataTypeAttribute(typeof(Question.QuestionMetadata))]
public partial class Question
{     
    internal sealed class QuestionMetadata
    {
        private QuestionMetadata()
        {
        }

        [Include]
        public EntityCollection<Answer> Answers { get; set; }

        public EntityCollection<AssignmentsQuestionsMapping> AssignmentsQuestionsMappings { get; set; }

        public int Marks { get; set; }

        public string QuestionDescription { get; set; }

        public long QuestionID { get; set; }

        public string QuestionTitle { get; set; }

        public EntityCollection<UserQuestionAnsweredMapping> UserQuestionAnsweredMappings { get; set; }
    }
}

并且我在域服务中有以下查询

public IQueryable<Question> GetQuestionsByAssignmentId(long assignmentId)
        {
            var questions = from q in this.ObjectContext.Questions.Include("Answers")
                            join qam in this.ObjectContext.AssignmentsQuestionsMappings on q.QuestionID equals qam.QuestionID
                            join assign in this.ObjectContext.Assignments on qam.AssignmentID equals assign.AssignmentID
                            where assign.AssignmentID == assignmentId
                            select q;

            return questions;
        }

据我所知，如果您想在域服务查询中包含子实体，那么您可以在实体的元数据文件中设置 [Include] 属性并将其包含在通过 .Include("ChildEntityCollectionName") 查询。

我已经完成了这两个操作，但我仍然没有在客户端收到 ChildEntity Collection。 我缺少什么？

Answer 1

你快到了。您需要添加关联属性来帮助 WCF RIA 了解 Question 和 Answer 是如何关联的。

[Include]
[Association("Question_Answer", "QuestionID", "ParentQuestionID", IsForeginKey=false)]
public EntityCollection<Answer> Answers { get; set; }

这假设您的实体共享外键。

public class Question
{
...
    [Key]
    public long QuestionID { get; set;}
...
}

public class Answer
{
...
    [Key]
    public long AnswerID { get; set;}

    public long ParentQuestionID { get; set;}
...
}

您可以通过RIA服务查看更多信息：插入多个演示模型对象