asp.net-mvc - 对于强类型 View ，自定义类型的 MVC LINQ to SQL JOIN 失败

Question

我有两个表的简单数据模型，电子邮件和收件人，电子邮件可以发送给一个或多个收件人

我已经用这两个表设置了数据库，创建了 Linq to SQL 存储库，构建了 Controller 和强类型 View 。

当我想从数据库中选择所有记录时，这很好用

public IList<AllMailDetail> ListAll()
    {
        var allMail =
            from m in _datacontext.mail_receiveds
      join r in _datacontext.mail_recipients on m.DeliveryId equals r.DeliveryId
            select new AllMailDetail {
                                        DeliveryId = m.DeliveryId,
                                        MessageId = m.MessageId,
                                        SentFrom = m.SentFrom,
                                        FilePath = m.FilePath,
                                        FileName = m.FileName,
                                        SentDateTime = m.SentDateTime,
                                        ReceivedDateTime = m.ReceivedDateTime,
                                        Subject = m.Subject,
                                        SpamScore = m.SpamScore,
                                        IsSpam = m.IsSpam,
                                        SenderIP = m.SenderIP,
                                        Header = m.Header,
                                        SentTo = r.SentTo
                                      };

        return allMail.ToList <AllMailDetail>();
    }

自定义类型类

public class AllMailDetail
{
    public int DeliveryId { get; set; }
    public int? MessageId { get; set; }
    public string SentFrom { get; set; }
    public string FilePath { get; set; }
    public string FileName { get; set; }
    public string SentDateTime { get; set; }
    public DateTime ReceivedDateTime { get; set; }
    public string Subject { get; set; }
    public byte? SpamScore { get; set; }
    public bool? IsSpam { get; set; }
    public string SenderIP { get; set; }
    public string Header { get; set; }
    public string SentTo { get; set; }
}

Controller 只是将内容从存储库发送到强类型 View

public ActionResult Index()
    {
        return View(_repository.ListAll());
    }

要从数据库中只获取一条邮件记录，我有以下代码，它接受一个 deliveryId

public IQueryable<AllMailDetail> GetMail(int? id)
    {
        var allMail =
            from m in _datacontext.mail_receiveds
            join r in _datacontext.mail_recipients 
            on m.DeliveryId equals r.DeliveryId
            where m.DeliveryId == id
            select new AllMailDetail
            {
                DeliveryId = m.DeliveryId,
                MessageId = m.MessageId,
                SentFrom = m.SentFrom,
                FilePath = m.FilePath,
                FileName = m.FileName,
                SentDateTime = m.SentDateTime,
                ReceivedDateTime = m.ReceivedDateTime,
                Subject = m.Subject,
                SpamScore = m.SpamScore,
                IsSpam = m.IsSpam,
                SenderIP = m.SenderIP,
                Header = m.Header,
                SentTo = r.SentTo
            };

        return allMail;
    }

及其 Controller 代码

public ActionResult Details(int? id)
    {       
        var mail = _repository.GetMail(id);

        if (mail == null)
            return View("NotFound");

        return View(mail);
    }

我一直在尝试通过在 aspx 页面顶部使用具有 Inherits="System.Web.Mvc.ViewPage 的强类型 View 来显示单个记录的输出，但出现以下错误

The model item passed into the dictionary is of type 'System.Data.Linq.DataQuery`1[projectMail.Models.AllMailDetail]' but this dictionary requires a model item of type projectMail.Models.AllMailDetail'.

经过大量搜索后，我修复了这个错误，发现这篇文章最有帮助
MVC LINQ to SQL Table Join Record Display

所以我的 View 不再是强类型的，我构建页面如下

<% foreach (projectMail.Models.AllMailDetail item in (IEnumerable)ViewData.Model)
    { %>

       ...items...

 <%  } %>

这很好用，但似乎还有很长的路要走。我想不通的是

为什么第二个查询需要是 IQueryable

为什么 View 是强类型时不起作用

如何使它与强类型 View 一起工作

这是在 MVC 中使用 LINQ to SQL 处理连接的最佳方式吗

Answer 1

嗯，试试 Controller

return View(_repository.GetMail( id).SingleOrDefault());

您正在尝试将 IQueryable 数据源绑定(bind)到 AllMailDetail View ，以上内容应该可以解决您的问题。