Deserialization stops on empty CDATA element

I have just encountered this bug when deserializing a document consisting mostly of CDATA elements. Some elements were empty and this is where the process would stop. All subsequent elements are ignored.

Excerpt from XML file:

    <Device fb="FB_Pneumatic2Pos" commandStruct="E_Pneumatic_Cmd">
      <Definition><![CDATA[	"#InstanceName#"(PlcCycleTime := "DB_Time".PlcCycleTime,
		OpMode := "DB_#Station#_Station".OpMode,
		Inactive := FALSE,
		I_SensorA := #I_SensorA#,
		I_SensorB := #I_SensorB#,
		C_TwoCoils := #C_TwoCoils#,
		C_ForceVentilate := #C_ForceVentilate#,
		C_Clamping := #C_Clamping#,
		C_PL := "E_PL".#C_PL#,
		C_TimeVentilate := T#200ms,
		C_TimeoutDuration := T#3s,
		C_WaitTimePosA := T#0ms,
		C_WaitTimePosB := T#0ms,
		Q_ValveA => #Q_ValveA#,
		Q_ValveB => #Q_ValveB#,
		Q_ValveOpenClamping => #Q_ValveOpenClamping#);]]></Definition>
      <DeviceDataDb><![CDATA[]]></DeviceDataDb>
      <ServiceHandler><![CDATA[	"FC_Pneumatic2Pos_Service_3Rows"(DeviceNo := #DeviceNo#,
		Row := #Row#,
		RowVisible := TRUE,
		DeviceName_Textlist := "E_Service3Row_DeviceNames"."#DeviceName#",
		ButtonTextPosA_Textlist := "E_Service_ButtonText"."#ActionA#",
		ButtonTextPosB_Textlist := "E_Service_ButtonText"."#ActionB#",
		I_PosA_2 := #I_SensorA2#,
		I_PosB_2 := #I_SensorB2#,
		IDB := #InstanceName#,
		Btn_DeActivateService := "DB_#Station#_Station".Buttons.Service);]]></ServiceHandler>
      <ParameterDb><![CDATA[]]></ParameterDb>
      <Releases><![CDATA[		"#InstanceName#".ReleasePosA := FALSE;
		"#InstanceName#".ReleasePosB := FALSE;]]></Releases>
      <CommandStart><![CDATA[]]></CommandStart>
      <WatchAndForceTable>
        <Capacity>16</Capacity>
        <WatchAndForceTableEntry name="Cmd" />
        <WatchAndForceTableEntry name="Execute" />
        <WatchAndForceTableEntry name="ExecState" />
        <WatchAndForceTableEntry name="ErrorCode" />
        <WatchAndForceTableEntry name="_State[1]" />
        <WatchAndForceTableEntry name="_StateName" />
        <WatchAndForceTableEntry name="I_SensorA" />
        <WatchAndForceTableEntry name="I_SensorB" />
        <WatchAndForceTableEntry name="_ValveA" />
        <WatchAndForceTableEntry name="_ValveB" />
        <WatchAndForceTableEntry name="_ValveOpenClamping" />
      </WatchAndForceTable>
    </Device>

This is the class I have previously serialized to the above XML.

    [DebuggerDisplay("{FB}")]
    [XmlRoot("Device")]
    public class SiemensDeviceTemplate : IDeviceTemplate
    {
        [XmlAttribute("fb")]
        public string FB { get; set; }

        [Verbatim]
        [XmlElement("Definition")]
        public string Definition { get; set; }

        [Verbatim]
        [XmlElement("DeviceDataDb")]
        public string DeviceDataDb { get; set; }

        [XmlElement("PlcTags")]
        public List<PlcTagTemplate> PlcTags { get; set; }

        [Verbatim]
        [XmlElement("ServiceHandler")]
        public string ServiceHandler { get; set; }
       
        [Verbatim]
        [XmlElement("ParameterDb")]
        public string ParameterDb { get; set; }

        [Verbatim]
        [XmlElement(ElementName = "Releases")]
        public string Releases { get; set; }

        [XmlAttribute("commandStruct")]
        public string CommandStruct { get; set; }

        [Verbatim]
        [XmlElement("CommandStart")]
        public string CommandStart { get; set; }

        [XmlElement("WatchAndForceTable")]
        public List<WatchAndForceTableTemplate> WatchAndForceTableEntires { get; set; }
    }

I have dug through the code and in XmlReader.cs method Content(). I have changed the following line to fix it and all tests passed except Issue271Test which seems to be unrelated to this issue.

		public string Content()
		{
			switch (_reader.NodeType)
			{
				case XmlNodeType.Attribute:
					return _reader.Value;
				default:
					if (_reader.IsEmptyElement && _reader.CanReadValueChunk)
					{
						Set();
						return string.Empty;
					}

					var isNull = IsSatisfiedBy(NullValueIdentity.Default);

					if (!isNull)
					{
						_reader.Read();
					}

					var result = isNull ? null : _reader.Value;

					if (!string.IsNullOrEmpty(result) || _reader.NodeType == XmlNodeType.CDATA) // added the node type check
					{
						_reader.Read();
						Set();
					}

					return result;
			}
		}					

Thanks for developing this project. 👍

[Mike-E-angelo]

Hah, that would do it! OK cool one less anomaly to worry about (I was fearing it might be some weird latent threading issue somehow).

Glad everything is to your liking. I will deploy this to NuGet next Tuesday and update here when it’s available. Please continue using the preview-build until that time.

[ms0815user]

I have reviewed the PR. It’s all good 👍. I also found out why #271 fails on my end. It’s a localisation issue because I ran it on a German system.

  Message: 
    Expected exception message to match the equivalent of 
    "Unknown/invalid member encountered: 'Show'. Line 4, position 7.", but 
    "Unknown/invalid member encountered: 'Show'. Zeile 4, Position 7." does not.