Question

我在类中进行了列表设置初始化并在主构造函数中添加了1个项目，但是从创建视图中添加它并不会因为某些原因将其添加到列表中。任何帮助将不胜感激。

public class PhoneBase
{
    public PhoneBase()
    {
        DateReleased = DateTime.Now;
        PhoneName = string.Empty;
        Manufacturer = string.Empty;
    }
    public int Id { get; set; }
    public string PhoneName { get; set; }
    public string Manufacturer { get; set; }
    public DateTime DateReleased { get; set; }
    public int MSRP { get; set; }
    public double ScreenSize { get; set; }
}

public class PhonesController : Controller
{
    private List<PhoneBase> Phones;
    public PhonesController()
    {
        Phones = new List<PhoneBase>();
        var priv = new PhoneBase();
        priv.Id = 1;
        priv.PhoneName = "Priv";
        priv.Manufacturer = "BlackBerry";
        priv.DateReleased = new DateTime(2015, 11, 6);
        priv.MSRP = 799;
        priv.ScreenSize = 5.43;
        Phones.Add(priv);
    }

public ActionResult Index()
    {
        return View(Phones);
    }

    // GET: Phones/Details/5
    public ActionResult Details(int id)
    {
        return View(Phones[id - 1]);
    }

这里我使用formcollections

通过Create view插入新的列表项

public ActionResult Create()
    {
        return View(new PhoneBase());
    }

    // POST: Phones/Create
    [HttpPost]
public ActionResult Create(FormCollection collection)
    {
        try
        {
            // TODO: Add insert logic here
            // configure the numbers; they come into the method as strings
            int msrp;
            double ss;
            bool isNumber;

            // MSRP first...
            isNumber = Int32.TryParse(collection["MSRP"], out msrp);
            // next, the screensize...
            isNumber = double.TryParse(collection["ScreenSize"], out ss);

            // var newItem = new PhoneBase();
            Phones.Add(new PhoneBase
            {
                // configure the unique identifier
                Id = Phones.Count + 1,

                // configure the string properties
                PhoneName = collection["PhoneName"],
                Manufacturer = collection["manufacturer"],

                // configure the date; it comes into the method as a string
                DateReleased = Convert.ToDateTime(collection["DateReleased"]),

                MSRP = msrp,
                ScreenSize = ss
            });


            //show results. using the existing Details view
            return View("Details", Phones[Phones.Count - 1]);
        }
        catch
        {
            return View();
        }
    }

查看整个列表并不会显示通过创建视图添加的任何项目。

Answer 1

因为 HTTP是无状态的！。 Phones是PhonesController中的变量，每个对该控制器的http请求（到它的各种操作方法）都会创建此类的新实例，因此，再次重新创建Phones变量，执行构造函数代码将一个Phone项添加到此集合。

您在创建操作中添加到Phones集合的项目将无法在下一个http请求中使用（对于电话/索引），因为它不知道之前的http请求是做什么的。< / p>

您需要保持数据在多个请求之间可用。您可以将其存储在数据库表/ XML文件/临时存储（如会话等）中。

ASP .net MVC列表没有更新

1 个答案: