Enable nullable on OpenXmlElement and OpenXmlCompositeElement (#849)

Author: twsouthwick

src/DocumentFormat.OpenXml/Framework/Metadata/ElementMetadata.cs

@@ -199,7 +199,7 @@ public Builder(Builder builder)
                 _builder = builder;
             }
 
-            public Builder<TElement> AddAttribute<TSimpleType>(byte nsId, string localName, Expression<Func<TElement, TSimpleType>> expression, Action<AttributeMetadata.Builder<TSimpleType>>? action = null)
+            public Builder<TElement> AddAttribute<TSimpleType>(byte nsId, string localName, Expression<Func<TElement, TSimpleType?>> expression, Action<AttributeMetadata.Builder<TSimpleType>>? action = null)
                 where TSimpleType : OpenXmlSimpleType, new()
             {
                 if (expression.Body is MemberExpression member)

src/DocumentFormat.OpenXml/Framework/Schema/CompiledParticle.cs

@@ -22,7 +22,7 @@ public CompiledParticle(ParticleConstraint particle)
 
         public ParticleConstraint Particle { get; }
 
-        public ParticlePath? Find(object obj)
+        public ParticlePath? Find(object? obj)
             => Find(obj?.GetType());
 
         public ParticlePath? Find(Type? type)

src/DocumentFormat.OpenXml/Framework/Schema/ParticleCollection.cs

@@ -157,7 +157,7 @@ public bool Contains(OpenXmlElement item)
         public struct Enumerator : IEnumerator<OpenXmlElement>
         {
             private readonly Type _type;
-            private OpenXmlElement _child;
+            private OpenXmlElement? _child;
 
             internal Enumerator(OpenXmlElement element, Type type)
             {
@@ -281,7 +281,7 @@ private void Advance()
                 {
                     if (Current is null)
                     {
-                        Current = _collection._element.FirstChild;
+                        Current = _collection._element.FirstChild!;
 
                         if (Current is null)
                         {
@@ -290,7 +290,7 @@ private void Advance()
                     }
                     else
                     {
-                        Current = Current.Next;
+                        Current = Current.Next!;
 
                         if (IsComplete)
                         {

src/DocumentFormat.OpenXml/OpenXmlChildElements.cs

@@ -22,9 +22,7 @@ public override IEnumerator<OpenXmlElement> GetEnumerator()
         {
             if (_container.HasChildren && _container.FirstChild is not null)
             {
-                for ( OpenXmlElement element = _container.FirstChild;
-                      element is not null;
-                      element = element.NextSibling() )
+                for (var element = _container.FirstChild; element is not null; element = element.NextSibling())
                 {
                     yield return element;
                 }
@@ -39,9 +37,7 @@ public override OpenXmlElement GetItem(int index)
         {
             if (_container.HasChildren)
             {
-                for (OpenXmlElement element = _container.FirstChild;
-                          element is not null;
-                          element = element.NextSibling())
+                for (var element = _container.FirstChild; element is not null; element = element.NextSibling())
                 {
                     if (index == 0)
                     {
@@ -63,9 +59,7 @@ public override int Count
                 int num = 0;
                 if (_container.HasChildren)
                 {
-                    for (OpenXmlElement element = _container.FirstChild;
-                              element is not null;
-                              element = element.NextSibling())
+                    for (var element = _container.FirstChild; element is not null; element = element.NextSibling())
                     {
                         num++;
                     }