NetDataContractSerializer.WriteStartObject Method (XmlWriter, Object)
Writes the opening XML element using an XmlWriter.
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 object to serialize has been exceeded. Check the MaxItemsInObjectGraph property.