Add support for repeated XML elements without a name attribute

src/libraries/Microsoft.Extensions.Configuration.Xml/src/XmlConfigurationElement.cs

@@ -0,0 +1,41 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Collections.Generic;
+
+namespace Microsoft.Extensions.Configuration.Xml
+{
+    internal class XmlConfigurationElement
+    {
+        public string ElementName { get; }
+
+        public string Name { get; }
+
+        /// <summary>
+        /// A composition of ElementName and Name, that serves as the basis for detecting siblings
+        /// </summary>
+        public string SiblingName { get; }
+
+        /// <summary>
+        /// The children of this element
+        /// </summary>
+        public IDictionary<string, List<XmlConfigurationElement>> ChildrenBySiblingName { get; set; }
+
+        /// <summary>
+        /// Performance optimization: do not initialize a dictionary and a list for elements with a single child
+        /// </summary>
+        public XmlConfigurationElement SingleChild { get; set; }
+
+        public XmlConfigurationElementTextContent TextContent { get; set; }
+
+        public List<XmlConfigurationElementAttributeValue> Attributes { get; set; }
+
+        public XmlConfigurationElement(string elementName, string name)
+        {
+            ElementName = elementName ?? throw new ArgumentNullException(nameof(elementName));
+            Name = name;
+            SiblingName = string.IsNullOrEmpty(Name) ? ElementName : ElementName + ":" + Name;
+        }
+    }
+}

src/libraries/Microsoft.Extensions.Configuration.Xml/src/XmlConfigurationElementAttributeValue.cs

@@ -0,0 +1,26 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+
+namespace Microsoft.Extensions.Configuration.Xml
+{
+    internal class XmlConfigurationElementAttributeValue
+    {
+        public XmlConfigurationElementAttributeValue(string attribute, string value, int? lineNumber, int? linePosition)
+        {
+            Attribute = attribute ?? throw new ArgumentNullException(nameof(attribute));
+            Value = value ?? throw new ArgumentNullException(nameof(value));
+            LineNumber = lineNumber;
+            LinePosition = linePosition;
+        }
+
+        public string Attribute { get; }
+
+        public string Value { get; }
+
+        public int? LineNumber { get; }
+
+        public int? LinePosition { get; }
+    }
+}

src/libraries/Microsoft.Extensions.Configuration.Xml/src/XmlConfigurationElementTextContent.cs

@@ -0,0 +1,23 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+
+namespace Microsoft.Extensions.Configuration.Xml
+{
+    internal class XmlConfigurationElementTextContent
+    {
+        public XmlConfigurationElementTextContent(string textContent, int? linePosition, int? lineNumber)
+        {
+            TextContent = textContent ?? throw new ArgumentNullException(nameof(textContent));
+            LineNumber = lineNumber;
+            LinePosition = linePosition;
+        }
+
+        public string TextContent { get; }
+
+        public int? LineNumber { get; }
+
+        public int? LinePosition { get; }
+    }
+}