Remove unnecessary XmlQualifiedName allocations from XsdBuilder.ProcessElement/Attribute (#67045)

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

@@ -703,8 +703,10 @@ public BuilderNamespaceManager(XmlNamespaceManager nsMgr, XmlReader reader)
 
         internal override bool ProcessElement(string prefix, string name, string ns)
         {
-            XmlQualifiedName qname = new XmlQualifiedName(name, ns);
-            if (GetNextState(qname))
+            name ??= string.Empty;
+            ns ??= string.Empty;
+
+            if (GetNextState(name, ns))
             {
                 Push();
                 Debug.Assert(_currentEntry.InitFunc != null);
@@ -715,9 +717,9 @@ internal override bool ProcessElement(string prefix, string name, string ns)
             }
             else
             {
-                if (!IsSkipableElement(qname))
+                if (!IsSkipableElement())
                 {
-                    SendValidationEvent(SR.Sch_UnsupportedElement, qname.ToString());
+                    SendValidationEvent(SR.Sch_UnsupportedElement, XmlQualifiedName.ToString(name, ns));
                 }
                 return false;
             }
@@ -726,13 +728,15 @@ internal override bool ProcessElement(string prefix, string name, string ns)
 
         internal override void ProcessAttribute(string prefix, string name, string ns, string value)
         {
-            XmlQualifiedName qname = new XmlQualifiedName(name, ns);
+            name ??= string.Empty;
+            ns ??= string.Empty;
+
             if (_currentEntry.Attributes != null)
             {
                 for (int i = 0; i < _currentEntry.Attributes.Length; i++)
                 {
                     XsdAttributeEntry a = _currentEntry.Attributes[i];
-                    if (_schemaNames.TokenToQName[(int)a.Attribute].Equals(qname))
+                    if (_schemaNames.TokenToQName[(int)a.Attribute].Equals(name, ns))
                     {
                         try
                         {
@@ -768,7 +772,7 @@ internal override void ProcessAttribute(string prefix, string name, string ns, s
             }
             else
             {
-                SendValidationEvent(SR.Sch_UnsupportedAttribute, qname.ToString());
+                SendValidationEvent(SR.Sch_UnsupportedAttribute, XmlQualifiedName.ToString(name, ns));
             }
         }
 
@@ -2433,14 +2437,14 @@ private void AddParticle(XmlSchemaParticle particle)
             }
         }
 
-        private bool GetNextState(XmlQualifiedName qname)
+        private bool GetNextState(string name, string ns)
         {
             if (_currentEntry.NextStates != null)
             {
                 for (int i = 0; i < _currentEntry.NextStates.Length; ++i)
                 {
                     int state = (int)_currentEntry.NextStates[i];
-                    if (_schemaNames.TokenToQName[(int)s_schemaEntries[state].Name].Equals(qname))
+                    if (_schemaNames.TokenToQName[(int)s_schemaEntries[state].Name].Equals(name, ns))
                     {
                         _nextEntry = s_schemaEntries[state];
                         return true;
@@ -2451,7 +2455,7 @@ private bool GetNextState(XmlQualifiedName qname)
             return false;
         }
 
-        private bool IsSkipableElement(XmlQualifiedName qname)
+        private bool IsSkipableElement()
         {
             return ((CurrentElement == SchemaNames.Token.XsdDocumentation) ||
                     (CurrentElement == SchemaNames.Token.XsdAppInfo));

src/libraries/System.Private.Xml/src/System/Xml/XmlQualifiedName.cs

@@ -78,9 +78,11 @@ public override bool Equals([NotNullWhen(true)] object? other)
                 return true;
             }
 
-            return other is XmlQualifiedName qName && Name == qName.Name && Namespace == qName.Namespace;
+            return other is XmlQualifiedName qName && Equals(qName.Name, qName.Namespace);
         }
 
+        internal bool Equals(string name, string ns) => Name == name && Namespace == ns;
+
         /// <devdoc>
         ///    <para>[To be supplied.]</para>
         /// </devdoc>