將SQL查詢轉換為LINQ＃2

Question

我有一個數據庫包含兩個表： 用戶（ID用戶，名字，姓氏）和文件（idDoc，標題，到期日期，UserDoc），其中UserDoc是外鍵ID用戶

此外，我的C＃代碼中有兩個類：

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

和

 public class UserUI
{
    public int IdUser { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }

}

我需要轉換以下查詢：

select a.*, (select u.lastName from Users as u where u.idUser = a.UserDoc),(select u.firstName from Users as u where u.idUser = a.UserDoc)

從文檔中獲取，其中getdate（）<= a.expirationDate

我試過了，這是它的結果：

            var documents = (from d in DocumentDAO.GetDocument()
                             join k in UserDAO.GetUsers()
                             on d.UserDoc equals k.IdUser
                             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();

但是在調試器中，我注意到它沒有看到任何文檔（我檢查了一下，應該返回其中一個）

我也嘗試過這種方式：

            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();

但這給了我相同的結果

第三種方式：

            var documents = (from d in DocumentDAO.GetDocument()
                             from k in UserDAO.GetUsers()
                             where ((DateTime.Now <= d.ExpirationDate) && (k.IdUser == d.UserDoc))
                             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();

還是什么都沒有，但是如果我刪除（k.IdUser == d.UserDoc），它將向我顯示此文檔以及所有用戶

更新使用您的意見和想法，我這樣寫：

 var now = DateTime.Now;
        var documents = DocumentDAO.GetDocument()
                    .Where(d => d.ExpirationDate > now)
                    .Select(d => new DocumentUI
             {
                 Title = d.Title,
                 Description = d.Description,
                 DateOfAdd = d.DateOfAdd,
                 ExpirationDate = d.ExpirationDate,
                 UserDoc = d.UserDoc,
                 User = new UserUI {
                     FirstName =UserDAO.GetUsers().First().FirstName,
                     LastName = UserDAO.GetUsers().First().LastName
                           }
             }).ToList(); 

但我仍然不檢查UserDoc是否等於IdUser。 我應該在哪里添加？

Answer 1

因此，您應該具有以下內容：

var result = DocumentDAO.Where(d => d.expirationDate >= DateTime.Now).Select(d =>
                     new {
                       Document = d,
                       User = UserDAO.FirstOrDefault(u => u.idUser = d.UserDoc),
                       FirstName = User.firstName,
                       LastName = User.lastName,  
                     });

如果將EF用作ORM框架並配置了實體之間的適當關系，則您可能應該在Document具有User屬性。 在這種情況下，它將更加容易：

var result = context.Documents.Where(d => d.expirationDate >= DateTime.Now).Select(d =>
                         new {
                           Document = d,
                           FirstName = d.User.firstName,
                           LastName = d.User.lastName,  
                         });

Answer 2

vat now = DateTime.Now;
var result = DocumentDAO.GetDocument()
                        .Where(d => d.ExpirationDate > now)
                        .Select(d => new {
                                           doc = d,
                                           firstname = d.User.FirstName,
                                           lastname = d.User.LastName
                                       });

更新

為了返回DocumentUI的列表，請使用以下內容替換Select()語句：

.Select(d => new DocumentUI
                 {
                     Title = d.Title,
                     Description = d.Description,
                     DateOfAdd = d.DateOfAdd,
                     ExpirationDate = d.ExpirationDate,
                     UserDoc = d.UserDoc,
                     User = new UserUI { 
                                   FirstName = d.User.FirstName, 
                                   LastName = d.user.LastName
                               }
                 }).ToList();