实体框架深度查询多对多
实体框架深度查询多对多
提问于 2012-11-20 07:22:51
Entity Framework新手，试着弄清楚一些东西。我有下面列出的表格：
Users
---------
UserID
UserName
Roles
---------
RoleID
RoleName
UserRoles
---------
UserRoleID
UserID
RoleID我使用的是存储库模式。下面是一个存储库的示例(它们本质上都是相同的)
public class RoleRepository : IRoleRepository
{
private AuthorizationContext context = new AuthorizationContext();
public IQueryable<Role> Roles
{
get
{
return this.context.Roles;
}
}
public bool Save(Role pRole)
{
if (pRole.RoleID == 0 || pRole.RoleID == null)
{
context.Roles.Add(pRole);
}
context.SaveChanges();
return true;
}
public bool Delete(Role pRole)
{
context.Roles.Remove(pRole);
context.SaveChanges();
return true;
}
}现在，我想测试一个用户(通过UserName)是否属于一个角色(通过RoleName)。如何查询？我希望它是这样的，但它不起作用：
public bool IsUserInRole(string username, string roleName)
{
var repo = new UserRepository();
var user = repo.Users.FirstOrDefault(u => u.NetID == username && u.UserRoles.FirstOrDefault(r => r.Role.Name == roleName));
}如何查询该用户是否属于该角色？如果可能的话，我更喜欢使用谓词。
回答 2
Stack Overflow用户
回答已采纳
发布于 2012-11-20 08:22:39
我将像这样使用.Any函数：
public static bool IsUserInRole(string username, string roleName)
{
using(var roleRepository = new RoleRepository())
{
return roleRepository.Roles.Any(r => r.RoleName == roleName && r.UserRoles.Any(ur => ur.User.UserName == username));
}
}下面是一个控制台应用程序示例：
class Program
{
static void Main(string[] args)
{
var users = new List<string> { "A", "B", "C", "D" };
var roles = new List<string> { "User", "Admin", "Superuser"};
//User A has roles: User, Admin, Superuser
Debug.Assert(IsUserInRole(users[0], roles[0]) == true);
Debug.Assert(IsUserInRole(users[0], roles[1]) == true);
Debug.Assert(IsUserInRole(users[0], roles[2]) == true);
//User B has roles: User, Admin
Debug.Assert(IsUserInRole(users[1], roles[0]) == true);
Debug.Assert(IsUserInRole(users[1], roles[1]) == true);
Debug.Assert(IsUserInRole(users[1], roles[2]) == false);
//User C has roles: User
Debug.Assert(IsUserInRole(users[2], roles[0]) == true);
Debug.Assert(IsUserInRole(users[2], roles[1]) == false);
Debug.Assert(IsUserInRole(users[2], roles[2]) == false);
//User D has no roles
Debug.Assert(IsUserInRole(users[3], roles[0]) == false);
Debug.Assert(IsUserInRole(users[3], roles[1]) == false);
Debug.Assert(IsUserInRole(users[3], roles[2]) == false);
Debugger.Break();
}
public static bool IsUserInRole(string username, string roleName)
{
using(var roleRepository = new RoleRepository())
{
return roleRepository.Roles.Any(r => r.RoleName == roleName && r.UserRoles.Any(ur => ur.User.UserName == username));
}
}
}
public interface IRoleRepository : IDisposable
{
}
public class RoleRepository : IRoleRepository
{
private Context context = new Context();
public IQueryable<Role> Roles
{
get
{
return this.context.Roles.AsQueryable<Role>();
}
}
public void Dispose()
{
//Do nothing
}
}
public class Context : IDisposable
{
public IList<User> Users { get; set; }
public IList<Role> Roles { get; set; }
public IList<UserRole> UserRoles { get; set; }
public Context()
{
//Generate Some Fake Data
Users = new List<User>();
Users.Add(new User { UserID = 1, UserName = "A" });
Users.Add(new User { UserID = 2, UserName = "B" });
Users.Add(new User { UserID = 3, UserName = "C" });
Users.Add(new User { UserID = 4, UserName = "D" });
Roles = new List<Role>();
Roles.Add(new Role { RoleID = 1, RoleName = "User" });
Roles.Add(new Role { RoleID = 2, RoleName = "Admin" });
Roles.Add(new Role { RoleID = 3, RoleName = "Superuser" });
UserRoles = new List<UserRole>();
UserRoles.Add(new UserRole(1, Users[0], Roles[0]));
UserRoles.Add(new UserRole(1, Users[0], Roles[1]));
UserRoles.Add(new UserRole(1, Users[0], Roles[2]));
UserRoles.Add(new UserRole(1, Users[1], Roles[0]));
UserRoles.Add(new UserRole(1, Users[1], Roles[1]));
UserRoles.Add(new UserRole(1, Users[2], Roles[0]));
//User A has roles: User, Admin, Superuser
//User B has roles: User, Admin
//User C has roles: User
//User D has no roles
}
public void Dispose()
{
//Do nothing
}
}
public class User
{
public int UserID { get; set; }
public string UserName { get; set; }
public IList<UserRole> UserRoles { get; set; }
public User()
{
UserRoles = new List<UserRole>();
}
}
public class Role
{
public int RoleID { get; set; }
public string RoleName { get; set; }
public IList<UserRole> UserRoles { get; set; }
public Role()
{
UserRoles = new List<UserRole>();
}
}
public class UserRole
{
public int UserRoleID { get; set; }
public int UserId { get; set; }
public User User { get; set; }
public int RoleId { get; set; }
public Role Role { get; set; }
public UserRole(int id, User user, Role role)
{
UserRoleID = id;
UserId = user.UserID;
User = user;
user.UserRoles.Add(this);
RoleId = role.RoleID;
Role = role;
role.UserRoles.Add(this);
}
}Stack Overflow用户
发布于 2012-11-20 08:43:05
下面是您已经创建的修改后的IsUserInRole接口：
public bool IsUserInRole(string username, string roleName)
{
var repo = new UserRepository();
return repo.Users.Any(u => u.UserName == username && u.UserRoles.Any(userrole => userrole.Role.RoleName == roleName));
}您的应用程序接口的问题在于FirstOrDefault，它限制了导航属性。
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/13464209
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