Question

I have an entity which I need to save twice.
The first time is to set the ID.
This ID needs to be filled to calculate a signature and that signature is stored back to the entity.

See the following code:

var newEntity = new MyEntity 
    { 
        \\ set values 
    };

using (var db = MyContainer.CreateContainer())
{
    db.MyEntity.Add(newEntity);
    // Call SaveChanges() to set the ID.
    db.SaveChanges();

    // I need to do some calculation on the entity
    myEntity.Signature = CalculateSignature(myEntity);
    db.SaveChanges(); // <--- This causes the exception
}

This piece of code causes an InvalidOperationException, namely The relationship between the two objects cannot be defined because they are attached to different ObjectContext objects.

I don’t understand, am I not allowed to save the same entity twice? How would I go about achieving this?

Answer 1

I’m guessing that CalculateSignature creates a context too. Take a look at Entity Framework Multiple Object Contexts