Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Xml/System/Xml/Dom/XmlChildEnumerator.cs

@@ -0,0 +1,58 @@
+//------------------------------------------------------------------------------
+// <copyright file="XmlChildEnumerator.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>                                                                
+// <owner current="true" primary="true">[....]</owner>
+//------------------------------------------------------------------------------
+
+namespace System.Xml {
+    using System.Collections;
+
+    internal sealed class XmlChildEnumerator: IEnumerator {
+        internal XmlNode container;
+        internal XmlNode child;
+        internal bool isFirst;
+
+        internal XmlChildEnumerator( XmlNode container ) {
+            this.container = container;
+            this.child = container.FirstChild;
+            this.isFirst = true;
+        }
+
+        bool IEnumerator.MoveNext() {
+            return this.MoveNext();
+        }
+
+        internal bool MoveNext() {
+            if (isFirst) {
+                child = container.FirstChild;
+                isFirst = false;
+            }
+            else if (child != null) {
+                child = child.NextSibling;
+            }
+
+            return child != null;
+        }
+
+        void IEnumerator.Reset() {
+            isFirst = true;
+            child = container.FirstChild;
+        }
+
+        object IEnumerator.Current {
+            get {
+                return this.Current;
+            }
+        }
+
+        internal XmlNode Current {
+            get {
+                if (isFirst || child == null)
+                    throw new InvalidOperationException(Res.GetString(Res.Xml_InvalidOperation));
+
+                return child;
+            }
+        }
+    }
+}