Question

我花了一天时间解决这个问题。有这些权利：

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; }
}

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");
    });

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。所以我尝试添加Login to Users角色权限。但关系不会保存在数据库中 - RolesPrivilegesMapping表不包含id与Users角色和Login权限对应的记录。如果我直接添加 - 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" }
    }
}

如果数据库中存在所有实体，有人可以建议我如何只添加多对多关系吗？我正在使用EF 5.0。我用EF 4.3尝试了相同的结果。

Answer 1

如果您想要做的只是附加数据库中的现有条目，您可以更简单地做一些事情吗？

  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();
         }

Answer 2

谢谢。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;

实体代码首先保存多对多关系

2 个答案: