0

我花了一天的时间来解决这个问题。有这些实体：

public class UserRole
{
    [Key]
    public virtual int Id { get; set; }
    public virtual string Name { get; set; }
    public virtual ICollection<Privilege> Privileges { get; set; }
}

public class Privilege
{
    [Key]
    public virtual int Id { get; set; }
    public virtual string Name { get; set; }
    public virtual ICollection<UserRole> Roles { get; set; }
}

而这个配置在上下文中：

modelBuilder.Entity<UserRole>().HasMany<Privilege>(a => a.Privileges).WithMany(a => a.Roles)
.Map(m =>
    {
        m.MapLeftKey("RoleId");
        m.MapRightKey("PrivilegeId");
        m.ToTable("RolesPrivilegesMapping");
    });

而这个测试代码：

UserRole role;
//get role entity from context
//write privileges count
using (VaultContext context = new VaultContext(connectionString))
{
    role = context.UserRoles.Where(a => a.Name == "Users").FirstOrDefault();
    Console.WriteLine(role.Privileges.Count.ToString()); //writes 0
}

//make offline changes
//the privilege already exists in database
role.Privileges.Add(new Privilege() { Id = 1, Name = "Login" });

//save changes to database
using (VaultContext context = new VaultContext(connectionString))
{
    List<Privilege> privileges = new List<Privilege>();
    foreach (Privilege p in role.Privileges)
    { privileges.Add(p); }
    foreach (Privilege p in privileges)
    { context.Privileges.Attach(p); }
    role.Privileges.Clear();
    context.UserRoles.Attach(role);
    context.Entry(role).State = System.Data.EntityState.Modified;
    foreach (Privilege p in privileges)
    { role.Privileges.Add(context.Privileges.Find(p.Id)); }
    context.SaveChanges();
}

//reload the role entity
//write privileges count
using (VaultContext context = new VaultContext(connectionString))
{
    Console.WriteLine(context.UserRoles.Where(a => a.Name == "Users").FirstOrDefault().Privileges.Count.ToString()); //writes 0
}

用户角色和登录权限已在数据库中。所以我尝试将权限登录添加到用户角色。但是关系没有保存在数据库中 - RolesPrivilegesMapping 表不包含 ID 对应于用户角色和登录权限的记录。如果我只是直接添加 - 它可以工作，但它不是我的目标：

new UserRole() 
{ 
    Name = "Administrators", 
    Privileges = new List<Privilege>() 
    { 
        new Privilege() { Name = "Login" }
    }
}

如果所有实体都存在于数据库中，谁能建议我如何只添加多对多关系？我正在使用 EF 5.0。我已经用 EF 4.3 进行了尝试，结果相同。

4

2 回答 2

0

如果您只想在数据库中附加现有条目，您能做一些更简单的事情吗？

  using( VaultContext context = new VaultContext( ) )
         {
            role = context.UserRoles.FirstOrDefault(a => a.Name == "Users");
            Privilege p = context.Privileges.FirstOrDefault(pr => pr.Name == "Login");
            role.Privileges.Add(p);
            context.SaveChanges();
         }
于 2012-08-25T16:40:08.973 回答
0

谢谢你。这是我的解决方案：（角色离线更改）

UserRole dbRole = context.UserRoles.Find(role.Id);
dbRole.Privileges.Clear();
foreach (Privilege p in role.Privileges)
{
    dbRole.Privileges.Add(context.Privileges.Find(p.Id));
}
context.Entry(dbRole).State = System.Data.EntityState.Modified;
于 2012-08-28T10:45:02.903 回答