System.Xml.Schema.Preprocessor.GetBuildInSchema C# (CSharp) Method

        internal static XmlSchema GetBuildInSchema() {
            if (builtInSchemaForXmlNS == null) {
                XmlSchema tempSchema = new XmlSchema();
                tempSchema.TargetNamespace = XmlReservedNs.NsXml;
                tempSchema.Namespaces.Add("xml", XmlReservedNs.NsXml);
                
                XmlSchemaAttribute lang = new XmlSchemaAttribute();
                lang.Name = "lang";
                lang.SchemaTypeName = new XmlQualifiedName("language", XmlReservedNs.NsXs);
                tempSchema.Items.Add(lang);

                XmlSchemaAttribute xmlbase = new XmlSchemaAttribute();
                xmlbase.Name = "base";
                xmlbase.SchemaTypeName = new XmlQualifiedName("anyURI", XmlReservedNs.NsXs);
                tempSchema.Items.Add(xmlbase);

                XmlSchemaAttribute space = new XmlSchemaAttribute();
                space.Name = "space";
                    XmlSchemaSimpleType type = new XmlSchemaSimpleType();
                    XmlSchemaSimpleTypeRestriction r = new XmlSchemaSimpleTypeRestriction();
                    r.BaseTypeName = new XmlQualifiedName("NCName", XmlReservedNs.NsXs);
                    XmlSchemaEnumerationFacet space_default = new XmlSchemaEnumerationFacet();
                    space_default.Value = "default";
                    r.Facets.Add(space_default);
                    XmlSchemaEnumerationFacet space_preserve = new XmlSchemaEnumerationFacet();
                    space_preserve.Value = "preserve";
                    r.Facets.Add(space_preserve);
                    type.Content = r;
                    space.SchemaType = type;
                space.DefaultValue = "preserve";
                tempSchema.Items.Add(space);

                XmlSchemaAttributeGroup attributeGroup = new XmlSchemaAttributeGroup();
                attributeGroup.Name = "specialAttrs";
                XmlSchemaAttribute langRef = new XmlSchemaAttribute();
                langRef.RefName = new XmlQualifiedName("lang", XmlReservedNs.NsXml);
                attributeGroup.Attributes.Add(langRef);
                XmlSchemaAttribute spaceRef = new XmlSchemaAttribute();
                spaceRef.RefName = new XmlQualifiedName("space", XmlReservedNs.NsXml);
                attributeGroup.Attributes.Add(spaceRef);
                XmlSchemaAttribute baseRef = new XmlSchemaAttribute();
                baseRef.RefName = new XmlQualifiedName("base", XmlReservedNs.NsXml);
                attributeGroup.Attributes.Add(baseRef);
                tempSchema.Items.Add(attributeGroup);
                tempSchema.IsPreprocessed = true;
                tempSchema.CompileSchemaInSet(new NameTable(), null, null); //compile built-in schema

                Interlocked.CompareExchange<XmlSchema>(ref builtInSchemaForXmlNS, tempSchema, null);
            }
            return builtInSchemaForXmlNS; 
        }