Entity Framework - How to insert existing object inside of a new object

Question

I have the model visible below. My goal is to insert a new test with an existing Language and Facility. I keep getting the error saying the primary key I am trying to insert for Language and Facility already exists. It seems this method is trying to create a new Language and a new Facility. I just need to reference their ID's not create new.

Controller Method

dbContext.TestSubjects.Add(model.TestSubject);
    dbContext.SaveChanges();

    Test test = new Test
    {
        Language = model.Language,
        Facility = model.Facility,
        TestSubject = model.TestSubject,
        EvaluationState = "Not Started"
    };
    dbContext.Tests.Add(test);
    dbContext.SaveChanges();

Model:

public int Id { get; set; }
public string EvaluationState { get; set; }
public virtual Language Language { get; set; }
public virtual Organization Facility { get; set; }
public virtual TestSubject TestSubject { get; set; }

Answer 1

This example uses the foreign key by convention: see Entity Framework Code First Conventions for more details.

dbContext.TestSubjects.Add(model.TestSubject);
    dbContext.SaveChanges();

    Test test = new Test
    {
        // set your foreign key values
        LanguageId = 1,
        FacilityId = 12,
        TestSubjectId = 22,
        EvaluationState = "Not Started"
    };
    dbContext.Tests.Add(test);
    dbContext.SaveChanges();

You need to extend your model to tell Entity Framework what your foreign keys are like:

public int Id { get; set; }
public string EvaluationState { get; set; }
public int LanguageId { get; set; }
public virtual Language Language { get; set; }
public int FacilityId { get; set; }
public virtual Organization Facility { get; set; }
public int TestSubjectId { get; set; }
public virtual TestSubject TestSubject { get; set; }