c# - MVC4 C# 从数据库中填充 View 模型中的数据

Question

我有一个 View 模型需要来自两个模型人和地址的数据:

模型:

public class Person
{
   public int Id { get; set; }
   public string Name { get; set; }
   public int Age { get; set; }
   public int Gender { get; set; }
}

public class Address
{
   public int Id { get; set; }
   public string Street { get; set; }
   public int Zip { get; set; }
   public int PersonId {get; set; }
}

Viewmodel 本身就是

public class PersonAddViewModel
{
    public int Id { get; set; }
    public string Name { get; set; }
    public string Street { get; set; }
}

我已经尝试了几种方法来将数据放入 View 模型并将其传递给 View 。会有多条记录返回显示。

我最新的方法是这样填充 View 模型:

private AppContexts db = new AppContexts();
public ActionResult ListPeople()
{
    var model = new PersonAddViewModel();
    var people = db.Persons;
    foreach(Person p in people)
    {
        Address address = db.Addresses.SingleOrDefault(a => a.PersonId == p.Id)
        model.Id = p.Id;
        model.Name = p.Name;
        model.Street = address.Street;
    }
    return View(model.ToList());
}

我在“EntityCommandExecutionException 未被用户代码处理”的 Address address = db... 行中收到错误。

如何使用多个记录填充 View 模型并传递给 View ？

最终解决方案:

private AppContexts db = new AppContexts();
private AppContexts dbt = new AppContexts();
public ActionResult ListPeople()
{
    List<PersonAddViewModel> list = new List<PersonAddViewModel>();
    var people = db.Persons;
    foreach(Person p in people)
    {
        PersonAddViewModel model = new PersonAddViewModel();
        Address address = dbt.Addresses.SingleOrDefault(a => a.PersonId == p.Id)
        model.Id = p.Id;
        model.Name = p.Name;
        model.Street = address.Street;
    }
    return View(list);
}

Answer 1

首先，EntityCommandExecutionException 错误表明您的实体上下文或实体本身的定义存在错误。这是抛出异常，因为它发现数据库与您告诉它的方式不同。你需要弄清楚这个问题。

其次，关于执行此操作的正确方法，如果您的上下文配置正确，您显示的代码应该可以工作。但是，更好的方法是使用导航属性，只要您想要获取所有相关记录并且不指定其他 Where 子句参数即可。导航属性可能如下所示:

public class Person
{
   public int Id { get; set; }
   public string Name { get; set; }
   public int Age { get; set; }
   public int Gender { get; set; }

   public virtual Address Address { get; set; }
   // or possibly, if you want more than one address per person
   public virtual ICollection<Address> Addresses { get; set; }
}

public class Address
{
   public int Id { get; set; }
   public string Street { get; set; }
   public int Zip { get; set; }
   public int PersonId { get; set; }

   public virtual Person Person { get; set; }
}

然后你会简单地说:

public ActionResult ListPeople()
{
    var model = (from p in db.Persons // .Includes("Addresses") here?
                select new PersonAddViewModel() {
                    Id = p.Id,
                    Name = p.Name,
                    Street = p.Address.Street,
                    // or if collection
                    Street2 = p.Addresses.Select(a => a.Street).FirstOrDefault()
                });

    return View(model.ToList());
}