.net ef 3中多对多关系的复杂查询

在我的项目中，每个用户都有一个或多个组，每个组都有一个或多个角色 在用户登录之后，我想使用EntityFramework3获取该用户的角色。 这些就是我的模型

用户模型

public class User
    {

        public User()
        {
            userGroups = new List<UserGroup>();
        }
        public int Id { get; set; }

        [Display(Name = "UserName")]
        [Required]
        public string Username{get;set;}

        public ICollection<UserGroup> userGroups{get;set;}

        
    }

榜样

public class Role
    {
        public int Id{get;set;}

        public string roleName{get;set;}

        public string roleDescription{get;set;}
        public ICollection<RoleGroup> roleGroups{get;set;}
    }

我想要的是使用Id获取特定用户的所有角色

---

提前感谢。

您可以看到从用户到角色的路径相当清晰：

用户->用户组->角色组角色

所以它不是很复杂，查询可以是这样的：

//with lazy loading enabled
var userRoles = context.Users.FirstOrDefault(e => e.Id == someId)
                      ?.userGroups
                      ?.SelectMany(e => e.group.roleGroups)
                      ?.Select(e => e.role)?.ToList();

//with lazy loading disabled
var userRoles = context.Users.Where(e => e.Id == someId)
                       .SelectMany(e => e.userGroups)
                       .SelectMany(e => e.group.roleGroups)
                       .Select(e => e.role).ToList();

---

由于用户、组和角色表包含多对多关系，因此可以使用

Include

和

thenclude

方法加载相关数据。检查以下查询语句：

        //required using Microsoft.EntityFrameworkCore;
        var result = (_context.User
            .Include(c => c.userGroups)
            .ThenInclude(c => c.group)
            .ThenInclude(c => c.roleGroups)
            .ThenInclude(c => c.role)
            .Where(c=>c.Id ==1)
            .SelectMany(c => c.userGroups.SelectMany(d => d.group.roleGroups
                    .Select(e => new { UserName = c.Username, 
                            GroupName = e.group.groupName,  
                            RoleName = e.role.roleName })))).ToList();

数据表如下所示（我们可以看到用户“Tom”有两个角色：“Admin”和“Manager”）：

查询结果如下：

//with lazy loading enabled
var userRoles = context.Users.FirstOrDefault(e => e.Id == someId)
                      ?.userGroups
                      ?.SelectMany(e => e.group.roleGroups)
                      ?.Select(e => e.role)?.ToList();

//with lazy loading disabled
var userRoles = context.Users.Where(e => e.Id == someId)
                       .SelectMany(e => e.userGroups)
                       .SelectMany(e => e.group.roleGroups)
                       .Select(e => e.role).ToList();

//with lazy loading enabled
var userRoles = context.Users.FirstOrDefault(e => e.Id == someId)
                      ?.userGroups
                      ?.SelectMany(e => e.group.roleGroups)
                      ?.Select(e => e.role)?.ToList();

//with lazy loading disabled
var userRoles = context.Users.Where(e => e.Id == someId)
                       .SelectMany(e => e.userGroups)
                       .SelectMany(e => e.group.roleGroups)
                       .Select(e => e.role).ToList();

        //required using Microsoft.EntityFrameworkCore;
        var result = (_context.User
            .Include(c => c.userGroups)
            .ThenInclude(c => c.group)
            .ThenInclude(c => c.roleGroups)
            .ThenInclude(c => c.role)
            .Where(c=>c.Id ==1)
            .SelectMany(c => c.userGroups.SelectMany(d => d.group.roleGroups
                    .Select(e => new { UserName = c.Username, 
                            GroupName = e.group.groupName,  
                            RoleName = e.role.roleName })))).ToList();