Imported Upstream version 4.6.0.125

Former-commit-id: a2155e9bd80020e49e72e86c44da02a8ac0e57a4

mcs/class/referencesource/System.Web.Extensions/ClientServices/ConnectivityStatus.cs

@@ -0,0 +1,56 @@
+//------------------------------------------------------------------------------
+// <copyright file="ConnectivityStatus.cs" company="Microsoft">
+//     Copyright (c) Microsoft Corporation.  All rights reserved.
+// </copyright>
+//------------------------------------------------------------------------------
+namespace System.Web.ClientServices
+{
+    using System;
+    using System.IO;
+    using System.Security.Principal;
+    using System.Security;
+    using System.Security.Permissions;
+    using System.Security.AccessControl;
+
+    public static class ConnectivityStatus
+    {
+        public static bool IsOffline  {
+            get {
+                if (!_IsOfflineFetched)
+                    FetchIsOffline();
+                return _IsOffline;
+            }
+            set {
+                if (IsOffline != value) {
+                    _IsOffline = value;
+                    StoreIsOffline();
+                }
+            }
+        }
+
+        private static bool _IsOffline;
+        private static bool _IsOfflineFetched;
+
+        //[PermissionSet(SecurityAction.Assert, Unrestricted = true)]
+        private static void FetchIsOffline()
+        {
+            string path = Path.Combine(System.Windows.Forms.Application.UserAppDataPath, "AppIsOffline");
+            _IsOffline = File.Exists(path);
+            _IsOfflineFetched = true;
+        }
+
+
+        //[PermissionSet(SecurityAction.Assert, Unrestricted = true)]
+        private static void StoreIsOffline()
+        {
+            string path = Path.Combine(System.Windows.Forms.Application.UserAppDataPath, "AppIsOffline");
+            if (!_IsOffline) {
+                File.Delete(path);
+            } else {
+                using (FileStream fs = File.Create(path)) {
+                    fs.Write(new byte[0], 0, 0);
+                }
+            }
+        }
+    }
+}