Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Web/Configuration/DelayedRegex.cs

@@ -0,0 +1,51 @@
+//------------------------------------------------------------------------------
+// <copyright file="DelayedRegex.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>
+//------------------------------------------------------------------------------
+
+namespace System.Web.Configuration {
+
+    using System.Collections;
+    using System.Configuration;
+    using System.IO;
+    using System.Security;
+    using System.Security.Permissions;
+    using System.Text.RegularExpressions;
+    using System.Web.Configuration;
+    using System.Web.Util;
+    using System.Xml;
+
+    using Pair = System.Web.UI.Pair;
+
+    internal class DelayedRegex {
+
+        private String _regstring;
+        private Regex _regex;
+
+        internal DelayedRegex(String s) {
+            _regex = null;
+            _regstring = s;
+        }
+
+        internal Match Match(String s) {
+            EnsureRegex();
+            return _regex.Match(s);
+        }
+
+        internal int GroupNumberFromName(String name) {
+            EnsureRegex();
+            return _regex.GroupNumberFromName(name);
+        } 
+
+        internal void EnsureRegex() {
+            string regstring = _regstring;
+            if(_regex == null) {
+                _regex = new Regex(regstring);
+                //free original
+                _regstring = null;
+            }
+            return;
+        }
+    }
+}