System.Runtime.Serialization.XmlObjectSerializer.WriteNull C# (CSharp) Method

        internal static void WriteNull(XmlWriterDelegator writer)
        {
            writer.WriteAttributeBool(Globals.XsiPrefix, DictionaryGlobals.XsiNilLocalName, DictionaryGlobals.SchemaInstanceNamespace, true);
        }

 private void InternalWriteObjectContent(XmlWriterDelegator writer, object graph, DataContract contract, Hashtable surrogateDataContracts)
 {
     if (this.MaxItemsInObjectGraph == 0)
     {
         throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(XmlObjectSerializer.CreateSerializationException(System.Runtime.Serialization.SR.GetString("ExceededMaxItemsQuota", new object[] { this.MaxItemsInObjectGraph })));
     }
     if (base.IsRootXmlAny(this.rootName, contract))
     {
         throw DiagnosticUtility.ExceptionUtility.ThrowHelperError(XmlObjectSerializer.CreateSerializationException(System.Runtime.Serialization.SR.GetString("IsAnyNotSupportedByNetDataContractSerializer", new object[] { contract.UnderlyingType })));
     }
     if (graph == null)
     {
         XmlObjectSerializer.WriteNull(writer);
     }
     else
     {
         Type type = graph.GetType();
         if (contract.UnderlyingType != type)
         {
             contract = this.GetDataContract(graph, ref surrogateDataContracts);
         }
         XmlObjectSerializerWriteContext context = null;
         if (contract.CanContainReferences)
         {
             context = XmlObjectSerializerWriteContext.CreateContext(this, surrogateDataContracts);
             context.HandleGraphAtTopLevel(writer, graph, contract);
         }
         WriteClrTypeInfo(writer, contract, this.binder);
         contract.WriteXmlValue(writer, graph, context);
     }
 }