Question

我有以下实体。

    public class Paper
    {
        public int Id { get; set; }
        public string PaperCode { get; set; }
        ...
    }
    public class MCQPaper : Paper
    {
        public ICollection<MCQQuestion> Questions { get; set; }
    }
    public class MCQQuestion : Question
    {
        public int MCQPaperId { get; set; }
        public MCQPaper MCQPaper { get; set; }

        public int? MCQOptionId { get; set; }
        [ForeignKey("MCQOptionId")]
        public MCQOption TrueAnswer { get; set; }
        public ICollection<MCQOption> MCQOptions { get; set; }
    }
    public class MCQOption
    {
        public int Id { get; set; }
        public string OptionText { get; set; }
    }

我正在尝试基于唯一的papercode获取MCQPaper，但它总是给我空集的问题

这是我在存储库中的查询。

        public MCQPaper GetByPaperCode(string paperCode)
        {
            var ans = AppDbContext.MCQPapers
                .Where(paper => paper.PaperCode.Equals(paperCode))
                //.Include(paper => paper.Questions)
                //    .ThenInclude(que => que.MCQOptions)
                .Include(paper => paper.Questions)
                    .ThenInclude(que => que.MCQPaper)
                //.Include(paper => paper.Questions)
                //    .ThenInclude(que => que.TrueAnswer)
                .FirstOrDefault();
            return ans;
        }

在这里，我尝试了include（）和theninclude（）的各种组合，但是它们都不适合我

最后忽略语法错误（如果有的话）

先谢谢

Answer 1

发表评论并在Google上搜索后，我找到了解决方法

使用两个查询可以解决此问题，因为这里我在MCQQuestion和MCQOption之间具有循环依赖关系

所以解决方案是....

        public MCQPaper GetByPaperCode(string paperCode)
        {
            using var transaction = AppDbContext.Database.BeginTransaction();
            MCQPaper ans = new MCQPaper();
            try
            {
                ans = AppDbContext.MCQPapers
                .FirstOrDefault(paper => paper.PaperCode.Equals(paperCode));
                var questions = AppDbContext.MCQQuestions
                    .Include(que => que.MCQOptions)
                    .Where(que => que.MCQPaperId == ans.Id);
                ans.Questions = questions.ToList();
                transaction.Commit();
            }
            catch (Exception)
            {
                transaction.Rollback();
            }
            return ans;
        }

子表属性未在ef核心继承中获取

1 个答案: