Entity Inserts instead of Update - linq

Question

In my web i am retrieving a question object Including the subcategories it falls in and the language related data. It also has the QuestionID that is Primary Key for Question. I place this object in PageSession and modify the properties if user wants to.
using (var bo = new BL.QuestionBO())
{
var question = bo.Get(QuestionID);
PageSession.CurrentQuestion = question;
}
public Question Get(long QuestionID)
{
return DataSource.Questions
.Include(q => q.TransQuestions)
.Include(q => q.SubCategories)
.FirstOrDefault(q => q.QuestionID == QuestionID);
}
When I add the object back to the DataContext it adds a new object instead of updating the privious one.
DataSource.Questions.Add(QuestionEnt);
DataSource.SaveChanges();
Am i missing something or coding wrongly?
I have below areas in which i may be wrong.
The data context objects are different while retrieving an object.
I am using Questions.Add()
The proxy object may be don't care about insert/update.
Below is the class generated by .edmx
public partial class Question
{
public Question()
{
this.ChallengeDetails = new HashSet<ChallengeDetail>();
this.TransQuestions = new HashSet<TransQuestion>();
this.SubCategories = new HashSet<SubCategory>();
}
public long QuestionID { get; set; }
public int QuestionTypeID { get; set; }
public int Status { get; set; }
public int InsertedBy { get; set; }
public Nullable<int> ModifiedBy { get; set; }
public virtual ICollection<ChallengeDetail> ChallengeDetails { get; set; }
public virtual QuestionType QuestionType { get; set; }
public virtual ICollection<TransQuestion> TransQuestions { get; set; }
public virtual ICollection<SubCategory> SubCategories { get; set; }
}

Answer 1

Here is the reason.
The reason it happens is that when you use the DbSet.Add method (that
is, Screencasts.Add), not only is the state of the root entity marked
“Added,” but everything in the graph that the context was not
previously aware of is marked Added as well. Even though the developer
may be aware that the Topic has an existing Id value, Entity Framework
honors its EntityState (Added) and creates an Insert database command
for the Topic, regardless of the existing Id.
Source
To update an entity, here are the options you could do.
1. Option A, Change the State
DataSource.Entry(QuestionEnt).State = EntityState.Modified;
DataSource.SaveChanges();
2. Option B, Get the entity from context
var questionEntDb = DataSource.Questions.Find(QuestionEnt.QuestionID);
questionEntDb.PropertyA = QuestionEnt.PropertyA;
questionEntDb.PropertyB = QuestionEnt.PropertyB;
questionEntDb.PropertyC = QuestionEnt.PropertyC;
DataSource.SaveChanges();
When you call Add method, even though it has the existing Id, the state of the entity becomes Added and if you call Attachafter calling Add, the state becomes Unchanged. In this case, it will not do the insert nor the update.
// State = Detached
DataSource.Questions.Add(QuestionEnt); // -> State = Added
DataSource.Questions.Attach(QuestionEnt); // -> State = Unchanged
DataSource.SaveChanges();