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Unable to attach entity that already exists

I get this error whenever I try to update one of my models. The update is pretty simple:

Todo bn = service.GetTodos().Single(t => t.todoId == 1);
bn.Note.noteTitle = "Something new";
service.SaveTodo(bn);

And the models have this structure:

  • A todo has a note
  • Todo has a list of tasks

I have a SaveTodo service that looks something like this:

public void SaveTodo ( TodoWrapper note )
{
    using (Repository repo = new Repository(new HpstrDataContext()))
    {
        if (note != null)
        {
            Todo todo = repo.Todos.SingleOrDefault(t => t.todoId == note.todoId);
            if (todo == null)
            {
                todo = new Todo();
                todo.Note = new Note();
            }
            todo.dueDate = note.dueDate;
            todo.priority = (short)note.priority;

            todo.Note.isTrashed = note.Note.isTrashed;
            todo.Note.permission = (short)note.Note.permission;
            todo.Note.noteTitle = note.Note.noteTitle;

            repo.SaveTodo(todo);
        }
    }
}

And the Repository SaveTodo method is pretty simple and looks like this:

public void SaveTodo ( Todo todo )
{
    if (todo.Note.noteId == 0)
    {
        dc.NoteTable.InsertOnSubmit(todo.Note);
    } else
    {
        dc.NoteTable.Attach(todo.Note);
        dc.NoteTable.Context.Refresh(RefreshMode.KeepCurrentValues , todo.Note);
    }
    if (todo.todoId == 0)
    {
        dc.TodoTable.InsertOnSubmit(todo);
    } else
    {
        dc.TodoTable.Attach(todo);
        dc.TodoTable.Context.Refresh(RefreshMode.KeepCurrentValues , todo);
    }
    dc.SubmitChanges();
}

The error occurs in this line in the repository: dc.NoteTable.Attach(todo.Note);. I tried many different things to make this work, but nothing works.

Any help would be greatly appreciated.

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1 answer

So, I solved the problem (hopefully). In my repository, I modified SaveTodo to look like this:

public void SaveTodo ( TodoWrapper note )
{
    using (Repository repo = new Repository(new HpstrDataContext()))
    {
        if (note != null)
        {
            Todo todo = repo.Todos.SingleOrDefault(t => t.todoId == note.todoId);
            if (todo == null)
            {
                todo = new Todo();
                todo.Note = new Note();
            }
            todo.dueDate = note.dueDate;
            todo.priority = (short)note.priority;
            todo.Note.isTrashed = note.Note.isTrashed;
            todo.Note.permission = (short)note.Note.permission;
            todo.Note.noteTitle = note.Note.noteTitle;
            foreach (TaskWrapper item in note.Tasks)
            {
                Task t = repo.Tasks.SingleOrDefault(task => task.tasksId == item.taskId);
                if (t == null)
                {
                    t = new Task();
                }
                t.Todo = todo;
                t.isCompleted = item.isCompleted;
                t.content = item.content;
                repo.SaveTask(t);
            }
        }
    }
}

- , () wcf.

:

public void SaveTask ( Task task )
{
    if (task.tasksId == 0)
    {
        dc.TaskTable.InsertOnSubmit(task);
    } else
    {
        dc.TaskTable.Context.Refresh(RefreshMode.KeepCurrentValues , task);
    }
    dc.SubmitChanges();
}

Attach, Todo , . , , . Todo , , . , , .

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