Help on debugging or troubleshooting serialization issues (SerializationException: Type System.Xml.XmlElement in Assembly System.Xml)

All,
I am stuck trying to convert my web application from using an InProc session management to StateServer.

I have specified all classes that I save to the session as Serializable and specified some of the member variables that cannot be serialized with the [NonSerialized] attribute. But I am still getting the error in the attached file. The stack trace being not very informative, I am not sure where the error is coming from or which class is not getting serialized correctly.

Appreciate any help on debugging or troubleshooting to figure out what causing this. I am not pasting any code as this is a big web application and not just a couple of classes and also since the stack trace is not pointing to any specific class.
Here is the stack trace.
 
[SerializationException: Type 'System.Xml.XmlElement' in Assembly 'System.Xml, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' is not marked as serializable.]
   System.Runtime.Serialization.FormatterServices.InternalGetSerializableMembers(RuntimeType type) +7733643
   System.Runtime.Serialization.FormatterServices.GetSerializableMembers(Type type, StreamingContext context) +258
   System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.InitMemberInfo() +111
   System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.InitSerialize(Object obj, ISurrogateSelector surrogateSelector, StreamingContext context, SerObjectInfoInit serObjectInfoInit, IFormatterConverter converter, ObjectWriter objectWriter) +161
   System.Runtime.Serialization.Formatters.Binary.WriteObjectInfo.Serialize(Object obj, ISurrogateSelector surrogateSelector, StreamingContext context, SerObjectInfoInit serObjectInfoInit, IFormatterConverter converter, ObjectWriter objectWriter) +51
   System.Runtime.Serialization.Formatters.Binary.ObjectWriter.Write(WriteObjectInfo objectInfo, NameInfo memberNameInfo, NameInfo typeNameInfo) +7631620
   System.Runtime.Serialization.Formatters.Binary.ObjectWriter.Serialize(Object graph, Header[] inHeaders, __BinaryWriter serWriter, Boolean fCheck) +461
   System.Runtime.Serialization.Formatters.Binary.BinaryFormatter.Serialize(Stream serializationStream, Object graph, Header[] headers, Boolean fCheck) +134
   System.Web.Util.AltSerialization.WriteValueToStream(Object value, BinaryWriter writer) +1577
 
[HttpException (0x80004005): Unable to serialize the session state. In 'StateServer' and 'SQLServer' mode, ASP.NET will serialize the session state objects, and as a result non-serializable objects or MarshalByRef objects are not permitted. The same restriction applies if similar serialization is done by the custom session state store in 'Custom' mode.]
   System.Web.Util.AltSerialization.WriteValueToStream(Object value, BinaryWriter writer) +1662
   System.Web.SessionState.SessionStateItemCollection.WriteValueToStreamWithAssert(Object value, BinaryWriter writer) +34
   System.Web.SessionState.SessionStateItemCollection.Serialize(BinaryWriter writer) +606
   System.Web.SessionState.SessionStateUtility.Serialize(SessionStateStoreData item, Stream stream) +239
   System.Web.SessionState.SessionStateUtility.SerializeStoreData(SessionStateStoreData item, Int32 initialStreamSize, Byte[]& buf, Int32& length) +72
   System.Web.SessionState.OutOfProcSessionStateStore.SetAndReleaseItemExclusive(HttpContext context, String id, SessionStateStoreData item, Object lockId, Boolean newItem) +87
   System.Web.SessionState.SessionStateModule.OnReleaseState(Object source, EventArgs eventArgs) +560
   System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +68
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +75

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Stateserver-Error.jpg
altumadminAsked:
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daveamourCommented:
What are you saving in your Sessions?
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altumadminAuthor Commented:
I figured out after some debugging that there was code that was trying to serialize an XmlNode.
0

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daveamourCommented:
And that isn't serializable?
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altumadminAuthor Commented:
Right, so I changed my code to get the xml as string and rereate the node again.
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daveamourCommented:
Ok nice one
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