XmlObjectSerializer.WriteObject Method (Stream, Object)
Writes the complete content (start, content, and end) of the object to the XML document or stream with the specified Stream.
Assembly: System.Runtime.Serialization (in System.Runtime.Serialization.dll)
the type being serialized does not conform to data contract rules. For example, the DataContractAttribute attribute has not been applied to the type.
there is a problem with the instance being serialized.
the maximum number of objects to serialize has been exceeded. Check the MaxItemsInObjectGraph property.