Create customizable comment encoding method (fixes #525)

Author: mganss

src/HtmlSanitizer/HtmlSanitizer.cs

@@ -99,6 +99,11 @@ public HtmlSanitizer(HtmlSanitizerOptions options)
             AllowedAtRules = new HashSet<CssRuleType>(options.AllowedAtRules);
         }
 
+        /// <summary>
+        /// Gets or sets the default <see cref="Action{IComment}"/> method that encodes comments.
+        /// </summary>
+        public Action<IComment> EncodeComment { get; set; } = DefaultEncodeComment;
+
         /// <summary>
         /// Gets or sets the default <see cref="Action{IElement}"/> method that encodes literal text content.
         /// </summary>
@@ -458,9 +463,7 @@ private void RemoveComments(INode context)
         {
             foreach (var comment in GetAllNodes(context).OfType<IComment>().ToList())
             {
-                var escapedText = comment.TextContent.Replace("<", "&lt;").Replace(">", "&gt;");
-                if (escapedText != comment.TextContent)
-                    comment.TextContent = escapedText;
+                EncodeComment(comment);
 
                 var e = new RemovingCommentEventArgs(comment);
                 OnRemovingComment(e);
@@ -470,6 +473,13 @@ private void RemoveComments(INode context)
             }
         }
 
+        private static void DefaultEncodeComment(IComment comment)
+        {
+            var escapedText = comment.TextContent.Replace("<", "&lt;").Replace(">", "&gt;");
+            if (escapedText != comment.TextContent)
+                comment.TextContent = escapedText;
+        }
+
         private static void DefaultEncodeLiteralTextElementContent(IElement tag)
         {
             var escapedHtml = tag.InnerHtml.Replace("<", "&lt;").Replace(">", "&gt;");