public IHttpActionResult Delete(int id)
 {
     if (id < 0)
     {
         return(BadRequest("Invalid customer id"));
     }
     using (var ctx = new CRUD_SampleEntities())
     {
         var existingCustomer = ctx.Customers.Where(c => c.Id == id).FirstOrDefault();
         if (existingCustomer == null)
         {
             return(NotFound());
         }
         ctx.Entry(existingCustomer).State = System.Data.Entity.EntityState.Deleted;
         ctx.SaveChanges();
     }
     return(Ok());
 }