When trying to update a List in a Model got an error: Violation of PRIMARY KEY constraint

Question

I'm developing an app for a Exams and other stuff... In my App I Add Questions and then i can add it to a Test. I'm also using Code First.

Here we have my Question Model:

public class Question
{
    public Question() {
        this.Tests = new HashSet<Test>();
    }

    public int QuestionId { get; set; }
    [Display(Name = "Descripción")]
    public string QuestionDescription { get; set; }
    [Display(Name = "Competencia")]
    public int ProfiencyId { get; set; }

    public virtual Proficiency Profiency { get; set; }
    public virtual ICollection<Test> Tests { get; set; }
}

And my Test Model:

public class Test
{
    public Test() {
        this.Questions = new HashSet<Question>();
    }

    public int TestId { get; set; }
    [Display(Name = "Descripción")]
    public string TestDescription { get; set; }
    [Display(Name = "Tipo de evaluación")]
    public EVALUATE_TO EvaluateTo { get; set; }

    public ICollection<Question> Questions { get; set; }
}

I Used Fluent API for the Many to Many relationship.

modelBuilder.Entity<Question>()
            .HasMany(question => question.Tests)
            .WithMany(test => test.Questions)
            .Map(ma =>
            {
                ma.MapLeftKey("QuestionId");
                ma.MapRightKey("TestId");
                ma.ToTable("QuestionTest");
            });

And I'm Updating the Questions of a Test in this method.

private void UpdateTestQuestions(string[] selectedQuestions, Test testToUpdate)
    {
        if (selectedQuestions == null)
        {
            testToUpdate.Questions = new List<Question>();
            return;
        }

        var selectedQuestionsHS = new HashSet<string>(selectedQuestions);
        var testQuestions = new HashSet<int>
            (testToUpdate.Questions.Select(c => c.QuestionId));
        foreach (var question in ApplicationDbContext.Questions)
        {
            if (selectedQuestionsHS.Contains(question.QuestionId.ToString()))
            {
                if (!testQuestions.Contains(question.QuestionId))
                {
                    if (!testToUpdate.Questions.Contains(question)) {
                        testToUpdate.Questions.Add(question);
                    }
                }
            }
            else
            {
                if (testQuestions.Contains(question.QuestionId))
                {
                    testToUpdate.Questions.Remove(question);
                }
            }
        }
    }

And when I Tried to save the database the application breaks and i get an error like this:

Violation of PRIMARY KEY constraint 'PK_dbo.QuestionTest'. Cannot insert duplicate key in object 'dbo.QuestionTest'. The duplicate key value is (1, 1).

I Was Following the Official Microsoft Documentation in: Microsoft Documentation MVC 5 Updating

And they said that we can modify a List just by changing his members and save it, but i get an error... Anyone know why? Thanks for reading! Hope you guys can help me.

Answer 1

After all the research and reading and trying a lot of things... I Just saw that mi List was not Virtual so that was the problem... I just answer if someone suffer the same thing...