设置关系时EF Core设置为空

Question

I'm using entity framework core in my app. I have some relations in my tables. The problem is that when I set the relations It saves the data, but when I want to read the data, that related fields are null :(

Due to code limitations on Stackoverflow, I link the project you go and see full code on GH.

Here is my code

AND

Here is the model

I'll be so thankful if you help me.

EDIT: Here is where I fill Data (line 140 to the end) The code

Answer 1

you should use .Include like this

  public static List<Question> GetQuestion()
        {
            List<Question> x = new List<Question>();
            using (var db = new Model())
            {
                x=db.Questions.Include("Course").Include("Answer").ToList();
            }

            return x;
        }

you can also view this link for why i used .Include Entity Framework Loading Related Entities