private void SendEnumRecentUser() { Task.Run(() => { Dictionary <string, int> result = new Dictionary <string, int>(); foreach (var record in recorder.GetHistoryList()) { result[record.userName] = (record.id); } StringBuilder sb = new StringBuilder(); foreach (var pair in result) { sb.AppendFormat("{0}->{1} || ", pair.Value, pair.Key); } SendResponseMessage(sb.ToString()); }); }