Windows Phone 8.1 SQLite delete error: no pk

im trying to delete a row in a sql db using SQLite for Windows Phone. This is my dbHelper Class:

public void DeleteContact(int Id)
    {
        using (var dbConn = new SQLiteConnection("models.db"))
        {

            var existingconact = dbConn.Query<item>("select * from item where Id =" + Id).FirstOrDefault();
            if (existingconact != null)
            {
                dbConn.RunInTransaction(() =>
                {
                    dbConn.Delete(existingconact);
                });
            }
        }
    }

And this is my code:

Database_controller controll = new Database_controller();
        int id = controll.ReadContact(infoVar.modelid).Id;
        controll.DeleteContact(id);

        Frame.GoBack();

But every time i tap the delete button in the app, this error pops up:

Cannot delete item: it has no PK

I've tried to add a Primary Key and Auto Increasment to the Id column of my table, because the guy in the tutorial i found, had the following picture in it:

Do you know how to fix this problem?