我的Linq查询（C＃）有什么问题？ [英] What is wrong with my Linq query (C#)?

问题描述

我有一个ViewModel;

I have a ViewModel;

 public class GetQuestionViewModel
{
    public IEnumerable<Question> Questions { get; set; }
    public IEnumerable<QuestionOption> QuestionOptions { get; set; }
    public int Id { get; set; }
    public Nullable<int> Options { get; set; }
    public string QuestionOption1 { get; set; }
    public Nullable<int> QuestionOptionRanking { get; set; }
    public string Question1 { get; set; }
    public int QuestionTypeId { get; set; }
    public Nullable<int> QuestionRanking { get; set; }
    public string Answer { get; set; }
}

我的查询结构如此;

And I have my Query structured as thus;

[HttpGet]
       public ActionResult ViewQuestion(int page = 1)
       {
           var userId = User.Identity.GetUserId();
           ICollection<GetQuestionViewModel> question = (from q in db.Questions
               join qo in db.QuestionOptions on q.Id equals qo.QuestionId
               join r in db.Responses on q.Id equals r.QuestionId
               where q.PageNumber == page
               select new GetQuestionViewModel
                {
                   QuestionOptionRanking = qo.QuestionOptionRanking,
                   Id = q.Id,
                   Options = q.Options,
                   QuestionTypeId = q.QuestionTypeId,
                   Question1 = q.Question1,
                   QuestionRanking = q.QuestionRanking,
                   Answer = r.Answer
                 }).ToList();

           ViewBag.PageNumber = page;
           return View(question);
       }

我的关系是许多QuestionOptions的一个问题，但到目前为止我还没有找到正确的语法返回任何QuestionOptions，尽管所有其他字段都包含我期望的数据。任何人都可以看到我做错了吗？

My relationships is one Question to many QuestionOptions but as yet I have not found the correct syntax to return ANY of the QuestionOptions although all the other fields contain the data I expect. Can anyone see what I am doing wrong, please?

推荐答案

你可以用这个来模拟



问题列表 - 主要列表

QuestionsOptions列表 - 次要列表

休息列表 - 次要列表



例如：加入1（问题列表和问题选项列表） - >它会给2行

加入1个结果加入Resonse列表 - >给出4行作为父级（第二次连接）（连接1有2行）

You can simulate with this

Questions List - main list
QuestionsOptions list - secondary list
Respose List - secondary list

for example: join 1 ( question list and question option list ) -> it will give 2 rows
join 1 results joined with Resonse list -> gives 4 rows as the parent(for second join) ( join 1 has 2 rows )

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using console_poc;

namespace oops1
{

    public class Db
    {
        public Db()
        {
            Questions = new List<Question>();
            Questions.Add(new Question() { Id = 1, Options = 1, PageNumber = 1, Question1 = "q1", QuestionRanking = 1, QuestionTypeId = 1 });


            QuestionOptions = new List<QuestionOption>();
            QuestionOptions.Add(new QuestionOption() { QuestionId = 1, QuestionOptionRanking = 1 });
            QuestionOptions.Add(new QuestionOption() { QuestionId = 1, QuestionOptionRanking = 2 });
            QuestionOptions.Add(new QuestionOption() { QuestionId = 2, QuestionOptionRanking = 3 });
            QuestionOptions.Add(new QuestionOption() { QuestionId = 2, QuestionOptionRanking = 4 });


            Responses = new List<Response>();
            Responses.Add(new Response() { Answer = "a1", QuestionId = 1 });

        }

        public List<QuestionOption> QuestionOptions { get; set; }
        public List<Question> Questions { get; set; }
        public List<Response> Responses { get; set; }
    }
    class Program
    {
        static void Main(string[] args)
        {

            int page = 1;

            Db db = new Db();
           // using lamda expression
           //var result =  db.Questions.Join(db.QuestionOptions, (k => k.Id), (k => k.QuestionId), (q, qo) => new { q, qo }).
           //     Join(db.Responses, (k => k.q.Id), (k => k.QuestionId), (qqo, r) => new { r, qqo }).Where(k=>k.qqo.q.PageNumber == page).Select(k =>
           //         new GetQuestionViewModel()
           //         {
           //             QuestionOptionRanking = k.qqo.qo.QuestionOptionRanking,
           //             Id = k.qqo.q.Id,
           //             Options = k.qqo.q.Options,
           //             QuestionTypeId = k.qqo.q.QuestionTypeId,
           //             Question1 = k.qqo.q.Question1,
           //             QuestionRanking = k.qqo.q.QuestionRanking,
           //             Answer = k.r.Answer
           //         }).ToList();


            var question = (from q in db.Questions
                            join qo in db.QuestionOptions on q.Id equals qo.QuestionId
                            join r in db.Responses on q.Id equals r.QuestionId
                            where q.PageNumber == page
                            select new GetQuestionViewModel
                             {
                                 QuestionOptionRanking = qo.QuestionOptionRanking,
                                 Id = q.Id,
                                 Options = q.Options,
                                 QuestionTypeId = q.QuestionTypeId,
                                 Question1 = q.Question1,
                                 QuestionRanking = q.QuestionRanking,
                                 Answer = r.Answer
                             }).ToList();


        }
    }
}

public class Question
{
    public int Id { get; set; }
    public int PageNumber { get; set; }
    public Nullable<int> Options { get; set; }
    public string Question1 { get; set; }
    public int QuestionTypeId { get; set; }
    public Nullable<int> QuestionRanking { get; set; }
}


public class QuestionOption
{
    public int QuestionId { get; set; }
    public Nullable<int> QuestionOptionRanking { get; set; }
}
public class Response
{
    public int QuestionId { get; set; }
    public string Answer { get; set; }
}

public class GetQuestionViewModel
{
    public IEnumerable<Question> Questions { get; set; }
    public IEnumerable<QuestionOption> QuestionOptions { get; set; }
    public int Id { get; set; }
    public Nullable<int> Options { get; set; }
    public string QuestionOption1 { get; set; }
    public Nullable<int> QuestionOptionRanking { get; set; }
    public string Question1 { get; set; }
    public int QuestionTypeId { get; set; }
    public Nullable<int> QuestionRanking { get; set; }
    public string Answer { get; set; }
}

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