Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Xml/System/Xml/XPath/Internal/ContextQuery.cs

@@ -0,0 +1,54 @@
+//------------------------------------------------------------------------------
+// <copyright file="ContextQuery.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>                                                                
+// <owner current="true" primary="true">[....]</owner>
+//------------------------------------------------------------------------------
+
+namespace MS.Internal.Xml.XPath {
+    using System;
+    using System.Xml;
+    using System.Xml.XPath;
+    using System.Diagnostics;
+
+    internal class ContextQuery : Query {
+        protected XPathNavigator contextNode;
+        
+        public ContextQuery() {
+            this.count = 0;
+        }
+        protected ContextQuery(ContextQuery other) : base(other) {
+            this.contextNode = other.contextNode;   // Don't need to clone here
+        }
+        public override void Reset() {
+            count = 0;
+        }
+
+        public override XPathNavigator Current { get { return contextNode; } }
+
+        public override object Evaluate(XPathNodeIterator context) {
+            contextNode = context.Current; // We don't clone here. Because we never move it.
+            count = 0;
+            return this; 
+        }
+
+        public override XPathNavigator Advance() {
+            if (count == 0) {
+                count = 1;
+                return contextNode;
+            }
+            return null;
+        }
+
+        public override XPathNavigator MatchNode(XPathNavigator current) {
+            return current;
+        }
+
+        public override XPathNodeIterator Clone() { return new ContextQuery(this); }
+
+        public override XPathResultType StaticType { get { return XPathResultType.NodeSet; } }
+        public override int CurrentPosition   { get { return count; } }
+        public override int Count             { get { return 1; } }
+        public override QueryProps Properties { get { return QueryProps.Merge | QueryProps.Cached | QueryProps.Position | QueryProps.Count; } }
+    }
+}