Question

我正在尝试在ef核心中插入多对多关系实体。

尝试插入时出现此错误：

Object reference not set to an instance of an object

这是实体：

public class ApplicationUser : IdentityUser
{
   ... other properties
  //many to many
  public ICollection<UserPermission> UserPermissions { get; set; }
}

public class Permission:EntityBase
{
 public string Name { get; set; }
 //many to many
 public ICollection<UserPermission> UserPermissions { get; set; }
}

 //join entity

public class UserPermission
{
    public string UserId { get; set; }
    public ApplicationUser User { get; set; }
    public int PermissionId { get; set; }
    public Permission Permission { get; set; }
}

这里也是Fluent-Api

        //user-permission many to many relationship
        builder.Entity<UserPermission>()
            .HasKey(up => new { up.UserId, up.PermissionId });

        builder.Entity<UserPermission>()
            .HasOne(up => up.User)
            .WithMany(p => p.UserPermissions)
            .HasForeignKey(x => x.UserId);

        builder.Entity<UserPermission>()
            .HasOne(p => p.Permission)
            .WithMany(u => u.UserPermissions)
            .HasForeignKey(x => x.PermissionId);

我在这里尝试了一种插入方法：

    public void AssignPermissions(ApplicationUser user,ICollection<int> permissions){
        try
        {
            if (user != null)
            {
                foreach (var per in permissions)
                {
                    var permission = _permissionRepository.GetById(per);
                    var userPermission = new UserPermission {
                        UserId = user.Id,
                        PermissionId = permission.Id
                    };
                    userPermission.Permission = permission;
                    userPermission.User = user;
                    user.UserPermissions.Add(userPermission);
                    _uow.Commit();
                }
            }
        }
        catch (Exception ex)
        {

            throw ex;
        }
    }

当我尝试在AssignPermissions方法中分配权限时，出现错误。

我该如何解决？

谢谢

Answer 1

我通过在Include查询中添加ApplicationUser参数来解决。

            var user = await _userManager.Users
                    .Include(x => x.UserPermissions)
                    .SingleAsync(x => x.Email == model.Email);

未将对象引用设置为对象ef核心实例的多对多插入

1 个答案: