System.Xml.Serialization.XmlReflectionImporter.GetTopLevelMapping C# (CSharp) Method

        internal static XmlTypeMapping GetTopLevelMapping(Type type, string defaultNamespace)
        {
            XmlAttributes a = new XmlAttributes(type.GetTypeInfo());
            TypeDesc typeDesc = new TypeScope().GetTypeDesc(type);
            ElementAccessor element = new ElementAccessor();

            if (typeDesc.Kind == TypeKind.Node)
            {
                element.Any = true;
            }
            else
            {
                string ns = a.XmlRoot == null ? defaultNamespace : a.XmlRoot.Namespace;
                string typeName = string.Empty;
                if (a.XmlType != null)
                    typeName = a.XmlType.TypeName;
                if (typeName.Length == 0)
                    typeName = type.Name;

                element.Name = XmlConvert.EncodeLocalName(typeName);
                element.Namespace = ns;
            }
            XmlTypeMapping mapping = new XmlTypeMapping(null, element);
            mapping.SetKeyInternal(XmlMapping.GenerateKey(type, a.XmlRoot, defaultNamespace));
            return mapping;
        }
    }

        /// <include file='doc\XmlSerializer.uex' path='docs/doc[@for="XmlSerializer.XmlSerializer1"]/*' />
        /// <devdoc>
        ///    <para>[To be supplied.]</para>
        /// </devdoc>
        public XmlSerializer(Type type, string defaultNamespace)
        {
            if (type == null)
            {
                throw new ArgumentNullException(nameof(type));
            }

            DefaultNamespace = defaultNamespace;
            rootType         = type;

            _mapping = GetKnownMapping(type, defaultNamespace);
            if (_mapping != null)
            {
                _primitiveType = type;
                return;
            }
#if !NET_NATIVE
            _tempAssembly = s_cache[defaultNamespace, type];
            if (_tempAssembly == null)
            {
                lock (s_cache)
                {
                    _tempAssembly = s_cache[defaultNamespace, type];
                    if (_tempAssembly == null)
                    {
                        {
                            // need to reflect and generate new serialization assembly
                            XmlReflectionImporter importer = new XmlReflectionImporter(defaultNamespace);
                            _mapping      = importer.ImportTypeMapping(type, null, defaultNamespace);
                            _tempAssembly = GenerateTempAssembly(_mapping, type, defaultNamespace);
                        }
                    }
                    s_cache.Add(defaultNamespace, type, _tempAssembly);
                }
            }
            if (_mapping == null)
            {
                _mapping = XmlReflectionImporter.GetTopLevelMapping(type, defaultNamespace);
            }
#else
            XmlSerializerImplementation contract = GetXmlSerializerContractFromGeneratedAssembly();

            if (contract != null)
            {
                this.innerSerializer = contract.GetSerializer(type);
            }
            else if (ReflectionMethodEnabled)
            {
                var importer = new XmlReflectionImporter(defaultNamespace);
                _mapping = importer.ImportTypeMapping(type, null, defaultNamespace);

                if (_mapping == null)
                {
                    _mapping = XmlReflectionImporter.GetTopLevelMapping(type, defaultNamespace);
                }
            }
#endif
        }