Add OpenXmlElement.IsValidChild method (#1915)

- closes #1212

Author: mikeebowen

src/DocumentFormat.OpenXml.Framework/OpenXmlCompositeElement.cs

@@ -3,7 +3,6 @@
 
 using DocumentFormat.OpenXml.Framework;
 using System;
-using System.Collections;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
@@ -534,6 +533,32 @@ public override void RemoveAllChildren()
 
         #endregion
 
+        /// <summary>
+        /// 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 <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)
+            {
+                return false;
+            }
+
+            foreach (var elem in Metadata.Children.Elements)
+            {
+                if (elem.Type.Name.Equals(element.Metadata.Type.Name))
+                {
+                    return true;
+                }
+            }
+
+            return false;
+        }
+
         /// <summary>
         /// Saves all of the current node's children to the specified XmlWriter.
         /// </summary>

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

@@ -1009,3 +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.OpenXmlCompositeElement.IsValidChild(DocumentFormat.OpenXml.OpenXmlElement! element) -> bool

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

@@ -8,7 +8,6 @@
 using DocumentFormat.OpenXml.Wordprocessing;
 using System;
 using System.IO;
-using System.Xml;
 using Xunit;
 
 namespace DocumentFormat.OpenXml.Tests
@@ -198,21 +197,6 @@ public void CanSetNullValue()
             Assert.Null(cell.Child);
         }
 
-        /// <summary>
-        /// A test for OpenXmlElement.GetOrAddFirstChild.
-        /// </summary>
-        [Fact]
-        public void GetOrAddFirstChildTest()
-        {
-            Paragraph p = new();
-            Run r = p.GetOrAddFirstChild<Run>();
-            Assert.NotNull(r);
-            Assert.Same(r, p.GetFirstChild<Run>());
-
-            var r2 = p.GetOrAddFirstChild<Run>();
-            Assert.Same(r, r2);
-        }
-
         private class WithChildElement : OpenXmlCompositeElement
         {
             public ChildElement Child
@@ -240,5 +224,61 @@ internal override void ConfigureMetadata(ElementMetadata.Builder builder)
                 builder.SetSchema(ElementType);
             }
         }
+
+        /// <summary>
+        /// A test for OpenXmlElement.GetOrAddFirstChild.
+        /// </summary>
+        [Fact]
+        public void GetOrAddFirstChildTest()
+        {
+            Paragraph p = new();
+            Run r = p.GetOrAddFirstChild<Run>();
+            Assert.NotNull(r);
+            Assert.Same(r, p.GetFirstChild<Run>());
+
+            var r2 = p.GetOrAddFirstChild<Run>();
+            Assert.Same(r, r2);
+        }
+
+        [Fact]
+        public void IsValidChild_ValidChild_ReturnsTrue()
+        {
+            // Arrange
+            Paragraph parentElement = new();
+            Run validChild = new();
+
+            // Act
+            bool result = parentElement.IsValidChild(validChild);
+
+            // Assert
+            Assert.True(result);
+        }
+
+        [Fact]
+        public void IsValidChild_InvalidChild_ReturnsFalse()
+        {
+            // Arrange
+            Paragraph parentElement = new();
+            Table invalidChild = new();
+
+            // Act
+            bool result = parentElement.IsValidChild(invalidChild);
+
+            // Assert
+            Assert.False(result);
+        }
+
+        [Fact]
+        public void IsValidChild_NullChild_ReturnsFalse()
+        {
+            // Arrange
+            Paragraph parentElement = new();
+
+            // Act
+            bool result = parentElement.IsValidChild(null);
+
+            // Assert
+            Assert.False(result);
+        }
     }
 }