Used a more memory-efficient technique to store the sparsely-used att…

…ributes of standardized elements.

Examples/AspNetPageEmitter/Program.cs

@@ -32,6 +32,10 @@ class TestDocument : IHtmlDocument
     Task IHtmlDocument.WriteBodyContentsAsync(HtmlWriter writer, CancellationToken cancellationToken)
     {
         writer.WriteElement("p", null, children => children.WriteText("Test bytes."));
+        writer.WriteElement("p", null, children =>
+        {
+            children.WriteElement("a", attributes => attributes.Write("href", "/"), children => children.WriteText("Test link."));
+        });
         writer.WriteScript(ValidatedScript.ForInlineSource("console.log('test')"));
         return Task.CompletedTask;
     }

HtmlUtilities/Validated/StandardElement.cs

@@ -1,4 +1,6 @@
-namespace HtmlUtilities.Validated;
+using System.Runtime.CompilerServices;
+
+namespace HtmlUtilities.Validated;
 
 /// <summary>
 /// Provides friendly syntax for use of standardized HTML elements.
@@ -7,17 +9,38 @@ public abstract class StandardElement
 {
     // Global attribute list from https://html.spec.whatwg.org/#global-attributes.
 
+    private readonly Dictionary<string, ValidatedAttributeValue> attributes = [];
+
+    private protected ValidatedAttributeValue? GetAttribute([CallerMemberName] string name = null!)
+        => attributes.TryGetValue(name, out var value) ? value : null;
+
+    private protected void SetAttribute(ValidatedAttributeValue? value, [CallerMemberName] string name = null!)
+    {
+        if (value is null)
+            return;
+
+        attributes[name] = value.GetValueOrDefault();
+    }
+
+    /// <summary>
+    /// All HTML elements may have the accesskey content attribute set
+    /// The accesskey attribute's value is used by the user agent as a guide for creating a keyboard shortcut that activates or focuses the element.
+    /// If specified, the value must be an ordered set of unique space-separated tokens none of which are identical to another token and each of which must be exactly one code point in length.
+    /// Source: https://html.spec.whatwg.org/#the-accesskey-attribute
+    /// </summary>
+    public ValidatedAttributeValue? AccessKey { get => GetAttribute(); set => SetAttribute(value); }
+
     /// <summary>
     /// Uniquely identifies an element.
     /// Source: https://dom.spec.whatwg.org/#concept-id
     /// </summary>
-    public ValidatedAttributeValue? Id { get; set; }
+    public ValidatedAttributeValue? Id { get => GetAttribute(); set => SetAttribute(value); }
 
     /// <summary>
     /// The title attribute represents advisory information for the element, such as would be appropriate for a tooltip.
     /// Source: https://html.spec.whatwg.org/#attr-title
     /// </summary>
-    public ValidatedAttributeValue? Title { get; set; }
+    public ValidatedAttributeValue? Title { get => GetAttribute(); set => SetAttribute(value); }
 
     private protected StandardElement()
     {
@@ -31,6 +54,7 @@ private protected StandardElement()
     /// <param name="writer">Receives the attributes.</param>
     private protected void Write(AttributeWriter writer)
     {
+        writer.Write(" accesskey"u8, AccessKey);
         writer.Write(" id"u8, Id);
         writer.Write(" title"u8, Title);
     }

HtmlUtilities/Validated/Standardized/Link.cs

@@ -8,12 +8,12 @@ public class Link : StandardElement
     /// <summary>
     /// Relationship between the document containing the hyperlink and the destination resource.
     /// </summary>
-    public string? Rel { get; set; }
+    public ValidatedAttributeValue? Rel { get => GetAttribute(); set => SetAttribute(value); }
 
     /// <summary>
     /// Address of the hyperlink.
     /// </summary>
-    public string? Href { get; set; }
+    public ValidatedAttributeValue? Href { get => GetAttribute(); set => SetAttribute(value); }
 
     internal sealed override void Write(HtmlWriter writer)
     {

HtmlUtilities/Validated/Standardized/Style.cs

@@ -13,7 +13,7 @@ public class Style : StandardElement
     /// <summary>
     /// Applicable media.
     /// </summary>
-    public ValidatedAttributeValue? Media { get; set; }
+    public ValidatedAttributeValue? Media { get => GetAttribute(); set => SetAttribute(value); }
 
     internal sealed override void Write(HtmlWriter writer)
     {