Question

我需要创建一个存储布尔值的变量。 is_following字段指示当前用户是否已签名（在其下进行授权）。我想要一个既好又快的解决方案。我的模型如下：

public class UserProfile
{
    [Required]
    public string FullName { get; set; }
    public string Description { get; set; }
    public int FollowerCount { get; set; } = 0;
    public int FollowingCount { get; set; } = 0;

    //I would like here to store a value to the status of subscription. This column must not be in the database.
    public bool IsFollowing { get; set; } = false; 

    [Key]
    public string UserId { get; set; }
    [ForeignKey("UserId")]
    [Required]
    protected virtual ApplicationUser User { get; set; }
}

下表（模型）：

public class Following
{
    [Key, Column(Order = 0)]
    public string UserId { get; set; }
    [ForeignKey("UserId")]
    public virtual ApplicationUser User { get; set; }

    [Key, Column(Order = 1)]
    public string FollowerId { get; set; }
    [ForeignKey("FollowerId")]
    public virtual ApplicationUser FollowerUser { get; set; }
}

首先想到的是为每个请求提出额外请求：

var following = db.Followings.Any(u => u.FollowerId == uId && u.UserId == currentUserId);

我不适合，因为用户样本的整个项目，我都要做这个额外的请求。

更新：

[NotMapped]
public virtual bool Is_Following { get
{
   var currentUser = HttpContext.Current.User.Identity.Name;

   using (ApplicationDbContext db = new ApplicationDbContext())
   {
        var userid = db.Users.FirstOrDefault(u => u.UserName == currentUser);
        if(userid!=null)
          return db.Followings.Any(u => u.FollowerId == UserId && u.UserId == UserId);
   }
   return false;
}

至少如何使用当前上下文而不创建新的上下文。

Answer 1

您是否阅读过有关存储库模式的内容？ https://www.asp.net/mvc/overview/older-versions/getting-started-with-ef-5-using-mvc-4/implementing-the-repository-and-unit-of-work-patterns-in-an-asp-net-mvc-application

它可以帮助您轻松实现您的需求。

Answer 2

它有效，但不是一个完美的解决方案：

    [NotMapped]
    public virtual bool Is_Following { get
        {
            var currentUser = HttpContext.Current.User.Identity.Name;
            if (currentUser == null) return false;

            using (ApplicationDbContext db = new ApplicationDbContext())
            {
                var userid = db.Users.FirstOrDefault(u => u.UserName == currentUser).Id;
                if(userid!=null)
                    return db.Followings.Any(u => u.FollowerId == userid && u.UserId == UserId);
            }
            return false;
        }
    }

实体框架模型中的附加查询

2 个答案: