Nullable: System.Xml, part 7 (Serialization)

src/libraries/System.Private.Xml/src/System/Xml/Schema/SchemaNamespacemanager.cs

@@ -24,7 +24,7 @@ public SchemaNamespaceManager(XmlSchemaObject node)
             { //Special case for the XML namespace
                 return XmlReservedNs.NsXml;
             }
-            Dictionary<string, string> namespaces;
+            Dictionary<string, string?> namespaces;
             for (XmlSchemaObject? current = _node; current != null; current = current.Parent)
             {
                 namespaces = current.Namespaces.Namespaces;
@@ -44,15 +44,15 @@ public SchemaNamespaceManager(XmlSchemaObject node)
             { //Special case for the XML namespace
                 return "xml";
             }
-            Dictionary<string, string> namespaces;
+            Dictionary<string, string?> namespaces;
             for (XmlSchemaObject? current = _node; current != null; current = current.Parent)
             {
                 namespaces = current.Namespaces.Namespaces;
                 if (namespaces != null && namespaces.Count > 0)
                 {
-                    foreach (KeyValuePair<string, string> entry in namespaces)
+                    foreach (KeyValuePair<string, string?> entry in namespaces)
                     {
-                        if (entry.Value.Equals(ns))
+                        if (entry.Value!.Equals(ns))
                         {
                             return entry.Key;
                         }

src/libraries/System.Private.Xml/src/System/Xml/Schema/XmlSchema.cs

@@ -56,17 +56,17 @@ public class XmlSchema : XmlSchemaObject
 
         public XmlSchema() { }
 
-        public static XmlSchema? Read(TextReader reader, ValidationEventHandler validationEventHandler)
+        public static XmlSchema? Read(TextReader reader, ValidationEventHandler? validationEventHandler)
         {
             return Read(new XmlTextReader(reader), validationEventHandler);
         }
 
-        public static XmlSchema? Read(Stream stream, ValidationEventHandler validationEventHandler)
+        public static XmlSchema? Read(Stream stream, ValidationEventHandler? validationEventHandler)
         {
             return Read(new XmlTextReader(stream), validationEventHandler);
         }
 
-        public static XmlSchema? Read(XmlReader reader, ValidationEventHandler validationEventHandler)
+        public static XmlSchema? Read(XmlReader reader, ValidationEventHandler? validationEventHandler)
         {
             XmlNameTable nameTable = reader.NameTable;
             Parser parser = new Parser(SchemaType.XSD, nameTable, new SchemaNames(nameTable), validationEventHandler);
@@ -136,7 +136,7 @@ public void Write(XmlWriter writer, XmlNamespaceManager? namespaceManager)
                 {
                     ns.Add("xs", XmlReservedNs.NsXs);
                 }
-                foreach (string? prefix in namespaceManager)
+                foreach (string prefix in namespaceManager)
                 {
                     if (prefix != "xml" && prefix != "xmlns")
                     {
@@ -146,7 +146,7 @@ public void Write(XmlWriter writer, XmlNamespaceManager? namespaceManager)
             }
             else if (this.Namespaces != null && this.Namespaces.Count > 0)
             {
-                Dictionary<string, string> serializerNS = this.Namespaces.Namespaces;
+                Dictionary<string, string?> serializerNS = this.Namespaces.Namespaces;
                 if (!serializerNS.ContainsKey("xs") && !serializerNS.ContainsValue(XmlReservedNs.NsXs))
                 { //Prefix xs not defined AND schema namespace not already mapped to a prefix
                     serializerNS.Add("xs", XmlReservedNs.NsXs);
@@ -166,15 +166,15 @@ public void Write(XmlWriter writer, XmlNamespaceManager? namespaceManager)
         }
 
         [Obsolete("Use System.Xml.Schema.XmlSchemaSet for schema compilation and validation. https://go.microsoft.com/fwlink/?linkid=14202")]
-        public void Compile(ValidationEventHandler validationEventHandler)
+        public void Compile(ValidationEventHandler? validationEventHandler)
         {
             SchemaInfo sInfo = new SchemaInfo();
             sInfo.SchemaType = SchemaType.XSD;
             CompileSchema(null, null, sInfo, null, validationEventHandler, NameTable, false);
         }
 
         [Obsolete("Use System.Xml.Schema.XmlSchemaSet for schema compilation and validation. https://go.microsoft.com/fwlink/?linkid=14202")]
-        public void Compile(ValidationEventHandler validationEventHandler, XmlResolver resolver)
+        public void Compile(ValidationEventHandler? validationEventHandler, XmlResolver? resolver)
         {
             SchemaInfo sInfo = new SchemaInfo();
             sInfo.SchemaType = SchemaType.XSD;

src/libraries/System.Private.Xml/src/System/Xml/Schema/XmlSchemaElement.cs

@@ -112,20 +112,23 @@ internal bool HasAbstractAttribute
         }
 
         [XmlAttribute("ref")]
+        [AllowNull]
         public XmlQualifiedName RefName
         {
             get { return _refName; }
             set { _refName = (value == null ? XmlQualifiedName.Empty : value); }
         }
 
         [XmlAttribute("substitutionGroup")]
+        [AllowNull]
         public XmlQualifiedName SubstitutionGroup
         {
             get { return _substitutionGroup; }
             set { _substitutionGroup = (value == null ? XmlQualifiedName.Empty : value); }
         }
 
         [XmlAttribute("type")]
+        [AllowNull]
         public XmlQualifiedName SchemaTypeName
         {
             get { return _typeName; }

src/libraries/System.Private.Xml/src/System/Xml/Schema/XsdBuilder.cs

@@ -795,7 +795,7 @@ internal override void StartChildren()
             {
                 if (_namespaces != null && _namespaces.Count > 0)
                 {
-                    _xso.Namespaces.Namespaces = _namespaces;
+                    _xso.Namespaces.Namespaces = _namespaces!;
                     _namespaces = null;
                 }
                 if (_unhandledAttributes.Count != 0)

src/libraries/System.Private.Xml/src/System/Xml/Serialization/CodeGenerationoptions.cs

@@ -1,6 +1,7 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+#nullable enable
 namespace System.Xml.Serialization
 {
     using System;