make IsValidChild virtual in OpenXmlElement and overridden in OpenXmlCompositeElement, return false instead of throw when element child to test is null

Author: mikeebowen

src/DocumentFormat.OpenXml.Framework/OpenXmlCompositeElement.cs

@@ -9,6 +9,7 @@
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
 using System.IO;
+using System.Linq;
 using System.Text;
 using System.Xml;
 
@@ -534,6 +535,21 @@ public override void RemoveAllChildren()
 
         #endregion
 
+        /// <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 override bool IsValidChild(OpenXmlElement element)
+        {
+            if (element is null)
+            {
+                return false;
+            }
+
+            return Metadata.Children.Elements.Any(el => el.Type.Name.Equals(element.Metadata.Type.Name));
+        }
+
         /// <summary>
         /// Saves all of the current node's children to the specified XmlWriter.
         /// </summary>

src/DocumentFormat.OpenXml.Framework/OpenXmlElement.cs

@@ -1335,14 +1335,9 @@ public bool IsBefore(OpenXmlElement element)
         /// </summary>
         /// <param name="element">The element to check.</param>
         /// <returns>True if the specified element is a valid child; otherwise, false.</returns>
-        public bool IsValidChild(OpenXmlElement element)
+        public virtual bool IsValidChild(OpenXmlElement element)
         {
-            if (element is null)
-            {
-                throw new ArgumentNullException(nameof(element));
-            }
-
-            return Metadata.Children.Elements.Any(el => el.Type.Name.Equals(element.Metadata.Type.Name));
+            return false;
         }
 
         private enum ElementOrder

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

@@ -1009,4 +1009,5 @@ 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
-DocumentFormat.OpenXml.OpenXmlElement.IsValidChild(DocumentFormat.OpenXml.OpenXmlElement! element) -> bool
+virtual DocumentFormat.OpenXml.OpenXmlElement.IsValidChild(DocumentFormat.OpenXml.OpenXmlElement! element) -> bool
+override DocumentFormat.OpenXml.OpenXmlCompositeElement.IsValidChild(DocumentFormat.OpenXml.OpenXmlElement! element) -> bool

test/DocumentFormat.OpenXml.Tests/ofapiTest/OpenXmlElementTest2.cs

@@ -245,11 +245,11 @@ public void GetOrAddFirstChildTest()
         public void IsValidChild_ValidChild_ReturnsTrue()
         {
             // Arrange
-            var parentElement = new Paragraph();
-            var validChild = new Run();
+            Paragraph parentElement = new();
+            Run validChild = new();
 
             // Act
-            var result = parentElement.IsValidChild(validChild);
+            bool result = parentElement.IsValidChild(validChild);
 
             // Assert
             Assert.True(result);
@@ -259,24 +259,27 @@ public void IsValidChild_ValidChild_ReturnsTrue()
         public void IsValidChild_InvalidChild_ReturnsFalse()
         {
             // Arrange
-            var parentElement = new Paragraph();
-            var invalidChild = new Table();
+            Paragraph parentElement = new();
+            Table invalidChild = new();
 
             // Act
-            var result = parentElement.IsValidChild(invalidChild);
+            bool result = parentElement.IsValidChild(invalidChild);
 
             // Assert
             Assert.False(result);
         }
 
         [Fact]
-        public void IsValidChild_NullChild_ThrowsArgumentNullException()
+        public void IsValidChild_NullChild_ReturnsFalse()
         {
             // Arrange
-            var parentElement = new Paragraph();
+            Paragraph parentElement = new();
 
-            // Act & Assert
-            Assert.Throws<ArgumentNullException>(() => parentElement.IsValidChild(null));
+            // Act
+            bool result = parentElement.IsValidChild(null);
+
+            // Assert
+            Assert.False(result);
         }
     }
 }