make OpenXmlCompositeElement.IsValidChild virtual

Author: mikeebowen

src/DocumentFormat.OpenXml.Framework/OpenXmlCompositeElement.cs

@@ -534,11 +534,14 @@ public override void RemoveAllChildren()
         #endregion
 
         /// <summary>
-        /// Determines if the specified element is a valid child of the current element.
+        /// Determines whether the specified <see cref="OpenXmlElement"/> is a valid child element
+        /// for this <see cref="OpenXmlCompositeElement"/> according to the schema definition.
         /// </summary>
-        /// <param name="element">The element to check.</param>
-        /// <returns>True if the specified element is a valid child; otherwise, false.</returns>
-        public override bool IsValidChild(OpenXmlElement element)
+        /// <param name="element">The <see cref="OpenXmlElement"/> to validate as a child.</param>
+        /// <returns>
+        /// <c>true</c> if the specified element is a valid child; otherwise, <c>false</c>.
+        /// </returns>
+        public virtual bool IsValidChild(OpenXmlElement element)
         {
             if (element is null)
             {

src/DocumentFormat.OpenXml.Framework/OpenXmlElement.cs

@@ -1330,16 +1330,6 @@ public bool IsBefore(OpenXmlElement element)
             return GetOrder(this, element) == ElementOrder.Before;
         }
 
-        /// <summary>
-        /// Determines if the specified element is a valid child of the current element.
-        /// </summary>
-        /// <param name="element">The element to check.</param>
-        /// <returns>True if the specified element is a valid child; otherwise, false.</returns>
-        public virtual bool IsValidChild(OpenXmlElement element)
-        {
-            return false;
-        }
-
         private enum ElementOrder
         {
             Same, // same element

src/DocumentFormat.OpenXml.Framework/PublicAPI/PublicAPI.Shipped.txt

@@ -1009,5 +1009,4 @@ DocumentFormat.OpenXml.OpenXmlPartWriterSettings.Encoding.set -> void
 DocumentFormat.OpenXml.OpenXmlPartWriterSettings.OpenXmlPartWriterSettings() -> void
 DocumentFormat.OpenXml.OpenXmlPartWriter.OpenXmlPartWriter(DocumentFormat.OpenXml.Packaging.OpenXmlPart! openXmlPart, DocumentFormat.OpenXml.OpenXmlPartWriterSettings! settings) -> void
 DocumentFormat.OpenXml.OpenXmlPartWriter.OpenXmlPartWriter(System.IO.Stream! partStream, DocumentFormat.OpenXml.OpenXmlPartWriterSettings! settings) -> void
-virtual DocumentFormat.OpenXml.OpenXmlElement.IsValidChild(DocumentFormat.OpenXml.OpenXmlElement! element) -> bool
-override DocumentFormat.OpenXml.OpenXmlCompositeElement.IsValidChild(DocumentFormat.OpenXml.OpenXmlElement! element) -> bool
+virtual DocumentFormat.OpenXml.OpenXmlCompositeElement.IsValidChild(DocumentFormat.OpenXml.OpenXmlElement! element) -> bool