public static string ToJson(string avatarname, List <AFriend> friends)
    {
        var lfriends = new List <List <string> >();

        foreach (var f in friends)
        {
            var fn    = f.OnGetFriendName(avatarname);
            var finfo = AFriend.OnGetFriendInfo(fn);
            if (finfo == null)
            {
                AOutput.LogError("Cannot find friend info of " + fn);
                continue;
            }
            var fs = new List <string>();
            fs.Add(InfoNameDefs.AvatarName);
            fs.Add(fn);
            fs.Add(InfoNameDefs.AvatarHead);
            fs.Add(finfo.head.ToString());
            fs.Add("accid");
            fs.Add(finfo.accid);
            lfriends.Add(fs);
        }
        return(AWebServerUtils.ToJsonArray(lfriends.ToArray()));
    }