Filter Child Object of a Collection

Question

First of all, I'm new to the EF-code first and .NET in general.

Im working on a mobile web app thats being built with MVC4, EF, JQuery, AutoMapper & other technologies and libraries.

This might be confusing, but I will do my best to explain it right.

I have the following pocos:

  public class Test
{
    [Key]
    public int TestId { get; set; }
    .
    .
    Other properties
    .
    .
    public virtual ICollection<Question> Questions { get; set; }
    public virtual ICollection<UserStatus> UserStatuses { get; set; }
}

public class UserStatus
{
    [Key]
    public int UserStatusId { get; set; }
    public int TestId { get; set; }
    public string Customer { get; set; }
    .
    .
    Other properties
    .
    .
}

public class Question
{
    [Key]
    public int QuestionId { get; set; }
    public int TestId { get; set; }
    .
    .
    Other properties
    .
    .
}

and in my context class i have:

protected override void OnModelCreating(DbModelBuilder modelBuilder)
{
    Database.SetInitializer<CmeContext>(null);

    modelBuilder.Entity<Test>()
        .HasKey(a => new { a.TestId })
        .HasMany(s => s.Questions);
    modelBuilder.Entity<Test>()
        .HasKey(a => new { a.TestId })
        .HasMany(s => s.UserStatuses);          
}

The above Test object has a one-to-many relationship to Question and UserStatus objects through TestId. Each Test has it's own set of questions which are 4 questions per test, and 20 userStatuses 5 per question). As the name implies the UserStatus table has user statuses; it let me know which question(s) from what test was answered by a user.

The code in the controller:

var filtered = (from test in _ctxCmeContext.Test.Include("UserStatus").Include("Question")
                where test.Program == "SomeProgram" && test.IssueDate.Value.Year == year && test.IssueDate.Value.Month == monthNumber 
                orderby test.IssueDate descending 
                select new { test,
                                                 Questions = test.Questions, 
                         UserStatuses =     test.UserStatuses.Where(x => x.Customer == currentUserId) });

As you see I have an anonymous class so I can get the UserStatuses collection filtered by currentUserId to get the statuses for the current user only. Everything works fine at this point.

Here's what I need to do:

Each question needs to know its own status, so it's a one-to-one relationship between the Question and UserStatus table

In my context class I added the following:

      modelBuilder.Entity<Question>()
     .HasRequired(x => x.UStatus)
     .WithOptional();

and in the Question Object I had:

                        public virtual UserStatus UStatus { get; set; }

and I also modified my linq statement as follows:

          var filtered = (from test in         _ctxCmeContext.Test.Include("UserStatus").Include("Question").Include("UStatus")
                where test.Program == "SomeProgram" &&   test.IssueDate.Value.Year == year && test.IssueDate.Value.Month == monthNumber 
                orderby test.IssueDate descending 
                select new { test, 
                             QuestionStatus =    test.Questions.Select(u=>u.UStatus), 
                             Questions = test.Questions, 
                             UserStatuses = test.UserStatuses.Where(x => x.Customer == currentUserId) }); 

The result:

the UStatus property had data for each question but it wasn't for the current user nor for the right test; it seemed to me that it just grabbed the first record it ecountered that had the same QuestionId from the Question table. No good.

so I changed the relationship to one-to-many:

In my context class I replaced:

    modelBuilder.Entity<Question>()
       .HasRequired(x => x.UStatus)
       .WithOptional();

with:

        modelBuilder.Entity<Question>()
           .HasKey(a => new { a.QuestionId })
           .HasMany(s => s.UStatus);

changed the UStatus property in the Question Object to:

   public virtual ICollection<UserStatus> UStatus { get; set; }

and removed the following from the linq statement

   QuestionStatus = test.Questions.Select(u=>u.UStatus), 

This time I was able to get some correct data but only for the first 4 questions, and the rest were null

I don't know what to do anymore. Help me please.

Answer 1

With the Schema/POCO you provided and by analyzing your story, what I can summarize is this:

You want to identify, which question(s) from what test was answered by a user?

If this is what you mean, then by assuming that lazy loading is enabled in your context I can suggest a query similar to this:

var questions = context.Questions.Where( q => q.Test.Program == "someProgram" 
                && q.Test.UserStatus.Any( us => us.UserId == currentUserId ));

It does the following:

1. Filter the questions which belongs to the Test someProgram
2. and having the UserStatus of the user currentUserId
3. Fetch the questions that satisfies this condition.

Hence in the questions collection you are having the answer for your problem.

My understanding of your problem might be wrong, but I believe it provides some hint to you.

Answer 2

在Question对象中，我创建了一个导航属性，返回到Test对象，从那里我可以知道每个问题的状态，因为UserStatus是Test对象中的一个子集合。