The property 'Id' is part of the object's key information and cannot be modified

Question

i\'m using Entity Framework 4.0 and having a silly problem that i can\'t figure out.

I have two tables:

1. Contact: Id (primary key), Value, ContactTypeId

Answer 1

This problem happens because you are referencing the same object more than once. This is not a limitation of EF, but rather a safety feature to ensure you are not inserting the same object with two different IDs. So to achieve what you are trying to do, is simply create a new object and add the newly created object to the database.

** This issue often happens inside loops. If you are using a while or foreach loop, make sure to have the New Created Object INSIDE the loop body.

try this:

Contact contact = dbContext.Contacts.Single(c => c.contactTypeId == 1234);
contact.contactTypeId = 4;
dbContext.AddObject(contact);
dbContext.SaveChanges();

Answer 2

Try

contact.ContactType = differentContactType;

or

contact.ContactTypeId = 3;

You are trying to set the Id of the ContactType (of the Contact) to 3.

Answer 3

first Remove next add

for simple

public static IEnumerable UserIntakeFoodEdit(FoodIntaked data)
        {
            DBContext db = new DBContext();
            var q = db.User_Food_UserIntakeFood.AsQueryable();
            var item = q.Where(f => f.PersonID == data.PersonID)
                  .Where(f => f.DateOfIntake == data.DateOfIntake)
                  .Where(f => f.MealTimeID == data.MealTimeIDOld)
                  .Where(f => f.NDB_No == data.NDB_No).FirstOrDefault();

            item.Amount = (decimal)data.Amount;
            item.WeightSeq = data.WeightSeq.ToString();
            item.TotalAmount = (decimal)data.TotalAmount;


            db.User_Food_UserIntakeFood.Remove(item);
            db.SaveChanges();

            item.MealTimeID = data.MealTimeID;//is key

            db.User_Food_UserIntakeFood.Add(item);
            db.SaveChanges();

            return "Edit";
        }

Answer 4

In my case the error was appearing as I removed the KEY attribute of the ID field.

// [Key]
public long Id { get; set; }

So just putting the attribute back in it's place, made everything working again!

[Key]
[DatabaseGenerated(DatabaseGeneratedOption.Identity)]
public long Id { get; set; }

Answer 5

In my case, I want to duplicate the object, but change the id, so I use this

Common.DataContext.Detach(object);

Work like a charm

Answer 6

in my case, i just set the primary key to table that was missing, re done the mappind edmx and it did work when you have the primary key tou would have only this

<PropertyRef Name="id" />

however if the primary key is not set, you would have

<PropertyRef Name="id" />
<PropertyRef Name="col1" />
<PropertyRef Name="col2" />

note that Juergen Fink answer is a work around