Question

我首先从数据库中加载了所有消息，然后选择了所需的内容。

但这不是全部加载。

var ldetails = _context.RegistrationUsers.Include（i => i.ListFriends）.ThenInclude（z => z.MessagesDetails）.SingleOrDefault（c => c.UserName == Context.User.Identity.Name）; < / p>

我只想按标准加载一条消息，但我经常遇到错误。请告诉我一种解决方法。

我尝试过

var ldetails = _context.RegistrationUsers.Include(i => i.ListFriends).ThenInclude(z=>z.MessagesDetails.SingleOrDefault(g=>g.TextMessage == messagesDetail.TextMessage)).SingleOrDefault(c => c.UserName == Context.User.Identity.Name);

但是我得到一个错误（

public class RegistrationUser
    {
        [Key]
        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
        public int PMId { get; set; }
        [Required]
        [Column(TypeName ="varchar(16)")]
        public string UserName { get; set; }
        [Required]
        [Column(TypeName = "varchar(16)")]
        public string Password { get; set; }
        [Column(TypeName = "varchar(480)")]
        public string Token { get; set; } 




        public ICollection<ListFriend> ListFriends { get; set; }


        public RegistrationUser()
        {
            ListFriends = new List<ListFriend>();

        }
    }


public class ListFriend
{
    [Key,Column(Order = 0)]

    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    public int UserId { get; set; }    
    [Required]
    [Column(TypeName ="varchar(16)")]
    public string UserFriendName { get; set; }



    public ICollection<MessagesDetail> MessagesDetails { get; set; 
    }

    public ListFriend()
    {

        MessagesDetails = new List<MessagesDetail>();
    }


}


public class MessagesDetail
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]

    [Key,Column(Order = 0)]
    public int PMIdMes     { get; set; }
    [Required]
    [Column(TypeName ="nvarchar(240)")]
    public string  TextMessage{ get; set; }
    [Required]
    [Column(TypeName = "varchar(16)")]
    public string SenderUser { get; set; }
    [Required]
    [Column(TypeName = "varchar(16)")]
    public string CatcherUser { get; set; } 
}


//My method

[Authorize]
public async Task DeleteMessage(string frend ,MessagesDetail 
messagesDetail)
        {

            var ldetails = _context.RegistrationUsers.Include(i => 
            i.ListFriends).ThenInclude(z=>z.MessagesDetails.
 SingleOrDefault(g=>g.TextMessage == messagesDetail.TextMessage)).
 SingleOrDefault(c => c.UserName == Context.User.Identity.Name);


//.....
         }


I expect to receive a message for the condition:

g=>g.TextMessage == messagesDetail.TextMessage;

Answer 1

您可能正在尝试过滤不支持的names(new_list) <- list或Include。您将必须使用IncludeThen创建投影：

Select

请查看此issue，以了解更多信息。

Answer 2

var pdetails =  _context.RegistrationUsers.SingleOrDefault(c=>c.Password==Context.User.Identity.Name);

            var nlk = _context.Entry(pdetails).Collection(n => n.ListFriends).Query().SelectMany(n => n.MessagesDetails)
                .Where(z => z.TextMessage == messagesDetail.TextMessage).ToList();

工作！

没有加载所有消息，我无法从数据库中获取消息

2 个答案: