無法創建類型爲''的常量值。只有原始類型或枚舉類型在此上下文中受支持。 ASP.NET MVC LINQ EF

Question

當試圖獲取要顯示的列表的值時，會出現不尋常的錯誤。我試圖讓每個用戶的數據庫中的所有項目數據。我認爲我的LINQ表達是錯誤的，但我不確定。

型號：

 public class ListModel 
    { 
     public List<StaffModel> StaffModelList { get; set; } 
    } 
     public class StaffModel 
    { 
     public FlexModel Flex { get; set; } 
     public List<Project> Projects { get; set; } 
    } 

     public partial class Project 
    { 
     public Project() 
     { 
      TimesheetEntries = new HashSet<TimesheetEntry>(); 
      UserProjects = new HashSet<UserProject>(); 
     } 

     [StringLength(50)] 
     public string ProjectId { get; set; } 

     [Required] 
     [StringLength(50)] 
     public string ProjectName { get; set; } 

     public int ProjectManager { get; set; } 

     public bool IsDebitable { get; set; } 

     [StringLength(50)] 
     public string Customer { get; set; } 

     public decimal EstimatedTotalHours { get; set; } 

     [Column(TypeName = "date")] 
     public DateTime ProjectStart { get; set; } 

     [Column(TypeName = "date")] 
     public DateTime? ProjectEnd { get; set; } 

     public virtual User User { get; set; } 

     public virtual ICollection<TimesheetEntry> TimesheetEntries { get; set; } 

     public virtual ICollection<UserProject> UserProjects { get; set; } 
    } 

查看：

@model Aviato.ViewModel.ListModel 
<table class="table"> 
    @foreach (var item in Model.StaffModelList) 
    { 
     <tr> 
      <td>@item.Flex.User.UserId</td> 
      <td>@item.Flex.FlexTime</td> 
      <td>@item.Flex.User.SocialSecurityNumber</td> 
      <td>@item.Flex.User.FirstName</td> 
      <td>@item.Flex.User.LastName</td> 
      <td>@item.Flex.User.Address1</td> 
      <td>@item.Flex.User.ZipCode</td> 
      <td>@item.Flex.User.City</td> 
      <td>@item.Flex.User.PhoneNumber1</td> 
      <td>@item.Flex.User.EmploymentStartDate</td> 
      <td>@item.Flex.User.Password</td> 

      @foreach (var items in item.Projects) 
      { 
       <td>@items.ProjectId</td> 
       <td>@items.ProjectName</td> 
       <td>@items.ProjectManager</td> 
       <td>@items.IsDebitable</td> 
       <td>@items.Customer</td> 
       <td>@items.EstimatedTotalHours</td> 
       <td>@items.ProjectStart</td> 
       <td>@items.ProjectEnd</td> 
      } 
     </tr> 
     @Html.ActionLink("Edit", "Edit", new { id = item.Flex.User.UserId }) 
     @Html.ActionLink("Delete", "Delete", new { id = item.Flex.User.UserId }) 
    } 
</table> 

控制器：

private readonly AviatoModel _db = new AviatoModel(); //Database 

public ActionResult Index() 
{ 
    var projects = _db.Projects.ToList(); 
    var users = _db.Users.Where(u => u.Projects == projects).ToList(); //Where the Error occurs if I use: "ToList();" 
    var model = new ListModel(); 
    var flexModel = new FlexModel(); 

    model.StaffModelList = new List<StaffModel>(); 

    foreach (var u in users) //Where the Error occurs if I dont use: "ToList();" 
    { 
     var staffModel = new StaffModel(); 

     staffModel.Projects = projects; 
     staffModel.Flex = flexModel; 
     staffModel.Flex.User = u; 
     staffModel.Flex.FlexTime = GetFlex.Flex(u.UserId); 
     model.StaffModelList.Add(staffModel); 
    } 

    return View(model); 
} 

請幫我...

Answer 1

這裏是你的問題：

var projects = _db.Projects.ToList(); 
    var users = _db.Users.Where(u => u.Projects == projects).ToList(); //Where the Error occurs if I use: "ToList();" 

而是嘗試：

var users = _db.Projects.Select(p => p.User).Distinct(); 

Answer 2

你的行動改變了這一點。這樣，無論用戶是否有任何項目，您都可以獲得所有用戶。

public ActionResult Index() 
{  
    var users = _db.Users.Include("Projects").ToList(); 

    var model = new ListModel(); 
    var flexModel = new FlexModel(); 

    model.StaffModelList = new List<StaffModel>(); 

    foreach (var u in users) 
    { 
     var staffModel = new StaffModel(); 

     staffModel.Projects.AddRange(u.Projects); //These are user specific projects. If there are no projects assigned to user, this list will be empty. 
     staffModel.Flex = flexModel; 
     staffModel.Flex.User = u; 
     staffModel.Flex.FlexTime = GetFlex.Flex(u.UserId); 
     model.StaffModelList.Add(staffModel); 
    } 

    return View(model); 
}