Web Service call results in an System.Xml.XmlException: '.', hexadecimal value 0x00

Question

I get the following unhandled exception thrown from my web service - this isn't anything to do with my code and it only happens intermittently when calling the server asynchronously many times. I've included the code response object I get returned as well as this is the only thing that comes back (in this cause the generic response is a List of String). Has anyone come across this before of know why a web service might throw this?

Entire Stack Trace:

System.Xml.XmlException: '.', hexadecimal value 0x00, is an invalid character. Line 4, position -88.
   at System.Xml.XmlTextReaderImpl.Throw(Exception e)
   at System.Xml.XmlTextReaderImpl.Throw(String res, String[] args)
   at System.Xml.XmlTextReaderImpl.Throw(Int32 pos, String res, String[] args)
   at System.Xml.XmlTextReaderImpl.ThrowInvalidChar(Int32 pos, Char invChar)
   at System.Xml.XmlTextReaderImpl.ParseNumericCharRefInline(Int32 startPos, Boolean expand, BufferBuilder internalSubsetBuilder, Int32& charCount, EntityType& entityType)
   at System.Xml.XmlTextReaderImpl.ParseText(Int32& startPos, Int32& endPos, Int32& outOrChars)
   at System.Xml.XmlTextReaderImpl.ParseText()
   at System.Xml.XmlTextReaderImpl.ParseElementContent()
   at System.Xml.XmlTextReaderImpl.Read()
   at System.Xml.XmlTextReader.Read()
   at System.Xml.XmlReader.ReadElementString()
   at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationReaderPartsLibraryService.Read29_GenericResponseOfListOfString(Boolean isNullable, Boolean checkType)
   at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationReaderPartsLibraryService.Read34_UploadPartsResponse()
   at Microsoft.Xml.Serialization.GeneratedAssembly.ArrayOfObjectSerializer5.Deserialize(XmlSerializationReader reader)
   at System.Xml.Serialization.XmlSerializer.Deserialize(XmlReader xmlReader, String encodingStyle, XmlDeserializationEvents events)

Simple Response object (pseudocode):

Public Class GenericResponse(Of T)
    Public Enum StateOptions

    Private _result As T
    Private _state As StateOptions
    Private _msg As String

    Public Property Result() As T
    Public Property State() As StateOptions
    Public Property Message() As String
End Class

I ran fiddler, but this was the only out of ordinary result I haven't seen, but I don't think it would cause the problem I'm experiencing?

<?xml version="1.0" encoding="utf-8"?><soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema"><soap:Body><UploadPartsResponse xmlns="http://autovhc.co.uk/"><UploadPartsResult><Result><string>--------------------------------------------------
01/06/2011 14:38:33
Upsert Exception
Backend sent unrecognized response type: &#x0;
   at Npgsql.NpgsqlState.&lt;ProcessBackendResponses_Ver_3&gt;d__a.MoveNext() in C:\projects\Npgsql2\src\Npgsql\NpgsqlState.cs:line 966
   at Npgsql.ForwardsOnlyDataReader.GetNextResponseObject() in C:\projects\Npgsql2\src\Npgsql\NpgsqlDataReader.cs:line 1163
   at Npgsql.ForwardsOnlyDataReader.GetNextRowDescription() in C:\projects\Npgsql2\src\Npgsql\NpgsqlDataReader.cs:line 1181
   at Npgsql.ForwardsOnlyDataReader.NextResult() in C:\projects\Npgsql2\src\Npgsql\NpgsqlDataReader.cs:line 1367
   at Npgsql.NpgsqlCommand.ExecuteNonQuery() in C:\projects\Npgsql2\src\Npgsql\NpgsqlCommand.cs:line 523
   at VHC.Connections.DataAccess2.DataAccess.sqlNonQuery(NpgsqlCommand sqlCmd, Boolean closeConnection) in E:\svn_repository\vhc.server.solution\vhc.connections\Tags\v_3_0_0_5\New\ConnectionProxys\DataAccess.vb:line 119
   at VHC.Connections.DataAccess2.DataAccess.sqlNonQuery(NpgsqlCommand sqlCmd) in E:\svn_repository\vhc.server.solution\vhc.connections\Tags\v_3_0_0_5\New\ConnectionProxys\DataAccess.vb:line 97
   at PartsLibServerSideClasses.DAO.PLM_PsaFormat_DAO.Update(PartLibraryPartTO part, Int32 entityref, NpgsqlConnection conn) in C:\Applications\PartsImporter\Import_Library-Stable\PartsLibServerSideClasses\DAO\PSA\PLM_PsaFormat_DAO.vb:line 61
   at PartsLibServerSideClasses.DAO.PLM_PsaFormat_DAO.Upsert(PartLibraryPartTO part, Int32 entityref) in C:\Applications\PartsImporter\Import_Library-Stable\PartsLibServerSideClasses\DAO\PSA\PLM_PsaFormat_DAO.vb:line 21
   at PartsLibServerSideClasses.Parsing.PartsLibraryManager.SubmitPartToLibrary(PartLibraryPartWorkSegmentContainer partContainer) in C:\Applications\PartsImporter\Import_Library-Stable\PartsLibServerSideClasses\BOL\PartsLibraryManager.vb:line 70
</string></Result><State>Fail</State></UploadPartsResult></UploadPartsResponse></soap:Body></soap:Envelope>

Answer 1

I have seen this before in bug code that did not encode or remove 0 when users were copying/pasting values into a database field from another application and the zero was then coming out for those records all the way to the xml parser.