单条多名称解析，单条中字符串逗号存储分割后的多用户解析

代码如下：

var userIds = cleanPoolDto.UserIds.Split(',').Select(a => long.Parse(a)).ToList();
List<Users> usersList = db.Queryable<Users>().Where(a => userIds.Contains(a.Id)).ToList();
foreach (var users in usersList)
{
    cleanPoolDto.UserNicknames += users.UserNickname + ",";
}
if (!string.IsNullOrWhiteSpace(cleanPoolDto.UserNicknames))
{
    cleanPoolDto.UserNicknames = cleanPoolDto.UserNicknames.TrimEnd(',');
}