Error when deserializing xml to an object: System.FormatException Input String was not in correct format

Question

Hello and thanks in advance for the help. I am having an issue when trying to deserialize an XElement into an object using an XmlSerializer and a StringReader. My code to deserialize is this:

/*deseierialize a single RegisterServerObject instance from xml*/
        static RegisterServerObject DeserializeSingleServerFromXml(XElement serverElement)
        {
            XmlSerializer deserializer = new XmlSerializer(typeof(RegisterServerObject));
            RegisterServerObject server;
            using (var reader = new StringReader(serverElement.ToString()))
                server = (RegisterServerObject)deserializer.Deserialize(reader);

            return server;
        }

I know the contents of the reader as revealed by the exception are:

<Server>
  <ServerID>11</ServerID>
  <GroupID />
  <ParentID>15</ParentID>
  <ServerName>IAProd1</ServerName>
  <User>admin</User>
  <UID>123</UID>
  <PWD>password</PWD>
  <Domain>InputAccel</Domain>
  <Location>Left</Location>
  <AssociatedModules>
    <Module>
      <ModId>1</ModId>
      <ServerId>11</ServerId>
      <ModName>TestModA</ModName>
      <ModuleStatus>1</ModuleStatus>
    </Module>
    <Module>
      <ModId>2</ModId>
      <ServerId>11</ServerId>
      <ModName>TestModB</ModName>
      <ModuleStatus>1</ModuleStatus>
    </Module>
    <Module>
      <ModId>9</ModId>
      <ServerId>11</ServerId>
      <ModName>TestModI</ModName>
      <ModuleStatus>1</ModuleStatus>
    </Module>
    <Module>
      <ModId>10</ModId>
      <ServerId>11</ServerId>
      <ModName>TestModJ</ModName>
      <ModuleStatus>1</ModuleStatus>
    </Module>
  </AssociatedModules>
</Server>

And my RegisterServerObject class looks like the following:

[XmlRoot("Server")]
    public class RegisterServerObject
    {
        public RegisterServerObject() { }

        public int ServerID { get; set; }

        public int GroupID { get; set; }

        public int ParentID { get; set; }

        public string ServerName { get; set; }

        public string User { get; set; }

        public int Uid { get; set; }

        public string Domain { get; set; }

        public string Location { get; set; }

        public List<RegisterModuleObject> AssociatedModules { get; set; }

    }

And at the risk of information overload the exact exception message I am getting is this:

System.InvalidOperationException: There is an error in XML document (4, 4). ---> System.FormatException: Input string was not in a correct format.
   at System.Number.StringToNumber(String str, NumberStyles options, NumberBuffer& number, NumberFormatInfo info, Boolean parseDecimal)
   at System.Number.ParseInt32(String s, NumberStyles style, NumberFormatInfo info)
   at System.Xml.XmlConvert.ToInt32(String s)
   at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationReaderRegisterServerObject.Read3_RegisterServerObject(Boolean isNullable, Boolean checkType)
   at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationReaderRegisterServerObject.Read4_Server()
   --- End of inner exception stack trace ---
   at System.Xml.Serialization.XmlSerializer.Deserialize(XmlReader xmlReader, String encodingStyle, Object events)
   at System.Xml.Serialization.XmlSerializer.Deserialize(XmlReader xmlReader, String encodingStyle)
   at System.Xml.Serialization.XmlSerializer.Deserialize(TextReader textReader)
   at SL_xMonitor_Frontend_RefactorV1.Views.RegisteringNewChildWindowV2.DeserializeSingleServerFromXml(XElement serverElement)
   at SL_xMonitor_Frontend_RefactorV1.Views.RegisteringNewChildWindowV2.modXmlClient_getAssociatedModulesCompleted(Object sender, getAssociatedModulesCompletedEventArgs e)
   at SL_xMonitor_Frontend_RefactorV1.XMLServersAndModulesServiceReference.XMLTablesAndModulesServiceClient.OngetAssociatedModulesCompleted(Object state)}

It seems there is an issue with converting the value of an xml element, ParentID maybe, into an int in order to instantiate the class, but I am not sure why that would be. Thank you in advance for the help!

Answer 1

The problem is that the property GroupID is declared as an integer, but its value is empty (<GroupID/>). One solution is to change the XML so that the value for that element is a valid integer:

<GroupID>0</GroupID>

Another solution would be to deserialize that value as a string, and convert to an integer which users of the type may consume:

    [XmlRoot("Server")]
    public class RegisterServerObject
    {
        public RegisterServerObject() { }

        public int ServerID { get; set; }

        [XmlIgnore]
        public int GroupID { get; set; }
        [XmlElement(ElementName = "GroupID")]
        public string GroupIDStr
        {
            get
            {
                return this.GroupID.ToString();
            }
            set
            {
                if (string.IsNullOrEmpty(value))
                {
                    this.GroupID = 0;
                }
                else
                {
                    this.GroupID = int.Parse(value);
                }
            }
        }

        public int ParentID { get; set; }

        public string ServerName { get; set; }

        public string User { get; set; }

        public int Uid { get; set; }

        public string Domain { get; set; }

        public string Location { get; set; }

        [XmlArray(ElementName = "AssociatedModules")]
        [XmlArrayItem(ElementName = "Module")]
        public List<RegisterModuleObject> AssociatedModules { get; set; }
    }

    public class RegisterModuleObject
    {
        public int ModId { get; set; }
        public int ServerId { get; set; }
        public string ModName { get; set; }
        public int ModuleStatus { get; set; }
    }