OPC UA how to read raw history values

ReadHistoryDlg.cs

private void ReadRaw(bool isReadModified)
        {
            ReadRawModifiedDetails details = new ReadRawModifiedDetails();
            details.StartTime = DateTime.MinValue;
            details.EndTime = DateTime.MinValue;
            details.IsReadModified = isReadModified;
            details.NumValuesPerNode = 0;
            details.ReturnBounds = ReturnBoundsCK.Checked;

            if (StartTimeCK.Checked)
            {
                details.StartTime = StartTimeDP.Value.ToUniversalTime();
            }

            if (EndTimeCK.Checked)
            {
                details.EndTime = EndTimeDP.Value.ToUniversalTime();
            }

            if (MaxReturnValuesCK.Checked)
            {
                details.NumValuesPerNode = (uint)MaxReturnValuesNP.Value;
            }

            HistoryReadValueId nodeToRead = new HistoryReadValueId();
            nodeToRead.NodeId = m_nodeId;

            if (m_result != null)
            {
                nodeToRead.ContinuationPoint = m_result.ContinuationPoint;
            }

            HistoryReadValueIdCollection nodesToRead = new HistoryReadValueIdCollection();
            nodesToRead.Add(nodeToRead);

            HistoryReadResultCollection results = null;
            DiagnosticInfoCollection diagnosticInfos = null;

            m_session.HistoryRead(
                null,
                new ExtensionObject(details),
                TimestampsToReturn.Source,
                false,
                nodesToRead,
                out results,
                out diagnosticInfos);

            Session.ValidateResponse(results, nodesToRead);
            Session.ValidateDiagnosticInfos(diagnosticInfos, nodesToRead);
            
            if (StatusCode.IsBad(results[0].StatusCode))
            {
                throw new ServiceResultException(results[0].StatusCode);
            }

            m_result = results[0];
       
            ShowResults();
        }