Linq sql-我应该将带“的短语放在哪里？”；其中；

这是我的问题，一个几乎有效的问题。我需要在这个查询中添加“where（k.IdUser==d.UserDoc。 添加此项时会出现问题。无论我将此项放在何处，它都会停止工作。此处没有“加入”选项。

 var documents = (from d in DocumentDAO.GetDocument()
                         from k in UserDAO.GetUsers()
                         where (DateTime.Now <= d.ExpirationDate)
                         select new DocumentUI
                         {
                             Title = d.Title,
                             Description = d.Description,
                             DateOfAdd = d.DateOfAdd,
                             ExpirationDate = d.ExpirationDate,
                             UserDoc = d.UserDoc,
                             User = new UserUI {
                                FirstName = k.FirstName, 
                                LastName = k.LastName}

                         }).ToList();

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下面的查询（与您的第一个查询相同）应该返回

列表

，前提是您有满足

的适当数据（（DateTime.Now，难道不可能没有
IdUser
等于
d.UserDoc
？：）不，在数据库中，我有一些字段，如title、description，其中一个字段是who add，它不是NULL，我检查它，有用户IDPerhaps，请尝试放置
UserDAO.GetUsers（）
首先在一个单独的、具体化的集合中，然后使用调试器查看，以验证在代码到达这里的那一刻，是否确实检索到了该用户。我尝试了，没有任何更改。它不应该更改任何内容。它应该向您提供我写过的信息。那么，您发现了什么？正如我所说的，join不是和option（我的任务要求它），此外，我只是尝试了一下，它不会改变它
var documents = (from d in DocumentDAO.GetDocument()
                     from k in UserDAO.GetUsers()
                     where ((DateTime.Now <= d.ExpirationDate) && (d.UserDoc == k.IdUser))
                     select new DocumentUI
                     {
                         Title = d.Title,
                         Description = d.Description,
                         DateOfAdd = d.DateOfAdd,
                         ExpirationDate = d.ExpirationDate,
                         UserDoc = d.UserDoc,
                         User = new UserUI {
                            FirstName = k.FirstName, 
                            LastName = k.LastName}

                     }).ToList();

var documents = (from d in DocumentDAO.GetDocument()
                     from k in UserDAO.GetUsers().Where(k => k.IdUser == d.UserDoc)
                     where (DateTime.Now <= d.ExpirationDate)
                     select new DocumentUI
                     {
                         Title = d.Title,
                         Description = d.Description,
                         DateOfAdd = d.DateOfAdd,
                         ExpirationDate = d.ExpirationDate,
                         UserDoc = d.UserDoc,
                         User = new UserUI {
                            FirstName = k.FirstName, 
                            LastName = k.LastName}

                     }).ToList();

public class DocumentUI
{
    public string Title { get; set; }
    public string Description { get; set; }
    public DateTime DateOfAdd { get; set; }
    public DateTime ExpirationDate { get; set; }
    public int UserDoc { get; set; }
    public UserUI User { get; set; }
}

var documents = (from d in DocumentDAO.GetDocument()
                 join k in UserDAO.GetUsers()
                 on d.UserDoc equals k.IdUser
                 where (d.ExpirationDate >= DateTime.Now)
                 select new DocumentUI
                 {
                     Title = d.Title,
                     Description = d.Description,
                     DateOfAdd = d.DateOfAdd,
                     ExpirationDate = d.ExpirationDate,
                     UserDoc = d.UserDoc,
                     User = new UserUI {
                        FirstName = k.FirstName, 
                        LastName = k.LastName}

                 }).ToList();