参数字典包含参数“id”的空条目

Question

我正在创建一个MVC应用程序。我在这样的视图之间传递一些数据：

public ActionResult AddGroup(AddGroupViewModel model)
        {
            var entities = new ClassDeclarationsDBEntities1();
            var model1 = new AddGroupViewModel();
            model1.Subjects = entities.Subjects.ToList();
            model1.Users = entities.Users.ToList();
            if (ModelState.IsValid)
            {
                var subj = entities.Subjects
                    .Where(b => b.name == model.subject_name)
                    .FirstOrDefault();
                int id = subj.class_id;
                return RedirectToAction("AddGroupsQty", "Account", new { qty = model.qty, subject_id = id});
            }
            return View(model1);
        }

并且：

public ActionResult AddGroupsQty(int qty, int id)
{
    ClassDeclarationsDBEntities1 entities = new ClassDeclarationsDBEntities1();

    var model = new AddGroupsQtyViewModel();
    model.subject_id = id;
    model.qty = qty;
    ClassDeclarationsDBEntities1 entities1=new ClassDeclarationsDBEntities1();
    var subj = entities1.Subjects
            .Where(b => b.class_id == model.subject_id)
            .FirstOrDefault();
    model.subject_name = subj.name;
    return View(model);
}

但不幸的是，我收到了这个错误：

  

参数字典包含参数'id'的空条目   方法的非可空类型'System.Int32'   'System.Web.Mvc.ActionResult AddGroupsQty（Int32，Int32）'in   'ClassDeclarationsThsesis.Controllers.AccountController'。可选的   参数必须是引用类型，可空类型或声明为   一个可选参数。 Nazwa参数：参数
     我该怎么做？

Answer 1

您的操作方法AddGroupsQty有2个参数qty和id，但是当您执行重定向时，您的查询字符串没有id！相反，它有一个叫subject_id

要修正错误，请将路线值项目从subject_id更改为id

return RedirectToAction("AddGroupsQty", "Account", new { qty = model.qty, id = id});

或者您可以将AddGroupsQty操作方法参数从id更改为subject_id（确保检查所有其他位置并根据需要修复查询字符串/路由值）