// Create a group @ message
var message = new Message
{
   message_conv_id = conv_id,
   message_conv_type = TIMConvType.kTIMConv_Group,
   message_elem_array = new List<Elem>{new Elem
   {
     elem_type = TIMElemType.kTIMElem_Text,
     text_elem_content = Input.text
   }},
   | message_group_at_user_array | UserID list of users that need to be mentioned (@) in the group message. To @all, pass in the `kImSDK_MesssageAtALL` field. |
};
StringBuilder messageId = new StringBuilder(128);
TIMResult res = TencentIMSDK.MsgSendMessage(conv_id, TIMConvType.kTIMConv_Group, message, messageId, (int code, string desc, string json_param, string user_data)=>{
 // Async message sending result
});

TIMResult res = TencentIMSDK.ConvGetConvList((int code, string desc, List<ConvInfo> info_list, string user_data)=>{
  foreach (ConvInfo info in info_list)
  {
    foreach (GroupAtInfo at_info in info.conv_group_at_info_array)
    {
      if (at_info.conv_group_at_info_at_type == TIMGroupAtType.kTIMGroup_At_Me) {
        // @me
      }
      if (at_info.conv_group_at_info_at_type == TIMGroupAtType.kTIMGroup_At_All) {
        // @all in the group
      }
      if (at_info.conv_group_at_info_at_type == TIMGroupAtType.kTIMGroup_At_All_At_ME) {
        // @all in the group and @me alone
      }
    }
  }
});