列表页回调，获取外键数据

var userids = entityPairs.Select(p => p.Item1.OwnerId).ToList();
            var userMapping = (context.Set<User>()
                .Where(u => userids.Contains(u.Id))
                .Select(u => new {
                    id = u.Id,
                    username = u.Username,
                    nickname = u.Nickname,
                }).ToDictionary(u => u.id, u => u));

pair.Item2["Username"] = userMapping.GetOrDefault((long)pair.Item1.OwnerId).nickname;

        /// <summary>
        /// 选择需要的字段
        /// </summary>
        [Tested("Common.Test.Admin.AdminAdminsControllerTest")]
        public void Select(EntireDbContext context,
            IList<Tuple<Admin, IDictionary<string, object>>> entityPairs) {
            // 获取关联的用户和角色名称
            var adminIds = entityPairs.Select(p => p.Item1.Id).ToList();
            var userMapping = (context.Set<User>()
                .Where(u => adminIds.Contains(u.Id))
                .Select(u => new {
                    id = u.Id,
                    username = u.Username,
                    nickname = u.Nickname,
                    roleId = u.RoleId,
                    roleName = u.Role.Name // 这里会转换成join
                }).ToDictionary(u => u.id, u => u));
            foreach (var pair in entityPairs) {
                pair.Item2["Id"] = pair.Item1.Id;
                pair.Item2["SuperAdmin"] = (
                    pair.Item1.SuperAdmin ? BooleanValues.True : BooleanValues.Null);
                pair.Item2["CreateTime"] = pair.Item1.CreateTime.ToClientTimeString();
                pair.Item2["Username"] = userMapping.GetOrDefault(pair.Item1.Id)?.username;
                pair.Item2["Nickname"] = userMapping.GetOrDefault(pair.Item1.Id)?.nickname;
                pair.Item2["RoleName"] = userMapping.GetOrDefault(pair.Item1.Id)?.roleName;
                pair.Item2["RoleId"] = userMapping.GetOrDefault(pair.Item1.Id)?.roleId;
            }
        }