gistfile1.cs

        // PUT api/Todo/5
        public HttpResponseMessage PutTodo(int id, Todo todo)
        {
            if (ModelState.IsValid && id == todo.TodoId)
            {
                db.Entry(todo).State = EntityState.Modified;

                try
                {
                    db.SaveChanges();
                }
                catch (DbUpdateConcurrencyException)
                {
                    return Request.CreateResponse(HttpStatusCode.NotFound);
                }

                return Request.CreateResponse(HttpStatusCode.OK);
            }
            else
            {
                return Request.CreateResponse(HttpStatusCode.BadRequest);
            }
        }