Update Foreign Key Object in EF6

Question

I have following Models:

public class DivorceCases
{
  [Key]
  [Required]
  public string case_id { get; set; }
  public string archived { get; set; }
  public virtual Plaintiff p { get; set; }
}

public class Plaintiff{
    [DatabaseGeneratedAttribute(DatabaseGeneratedOption.Identity)]
    public int id { get; set; }
    public string name { get; set; }
}

I am having a ModelView of DivorceCases for editing and in controller, I am using:

DivorceCases dcold = db.DivorceCase.Where(x => x.case_id == dc.case_id).Include(x => x.p).SingleOrDefault();
            dcold.p = dc.p;
            db.Entry(dcold).State = EntityState.Modified;
            db.SaveChanges();

When I update, instead of Updating the existing entry in Plaintiffs table, the EF6 inserts a new record in Plaintiffs table and updates the foreign key reference for this new record in DivorceCases table. What am I doing wrong? How do I get rid of that?

Answer 1

I got a solution after repeated debugging and hit and trials.

First of all I made a DBContextExtension Class like this:

public static T Modify<T>(this T t,T tnew)
    {
        PropertyInfo[] properties = typeof(T).GetProperties();
        foreach (PropertyInfo property in properties)
        {
            if (property.Name != "id" && (property.PropertyType==typeof(string) || property.PropertyType==typeof(DateTime)))
            {
                if (property.GetValue(tnew) != null)
                property.SetValue(t, property.GetValue(tnew));
            }
        }
        return t;
    }

Then for each foreign key referenced object, I called this Extension method and got 100% success.

DivorceCases dcold = db.DivorceCase.Where(x => x.case_id == dc.case_id).Include(x => x.p).SingleOrDefault();
            dcold = dcold.Modify(dc);
            dcold.p = dcold.p.Modify(dc.p);
            dcold.d = dcold.d.Modify(dc.d);
            db.SaveChanges();