toggle menu item Enable by WinINet state

shadowsocks-csharp/Controller/System/SystemProxy.cs

@@ -10,17 +10,12 @@ namespace Shadowsocks.Controller
     {
         private static Logger logger = LogManager.GetCurrentClassLogger();
 
-        private static string GetTimestamp(DateTime value)
-        {
-            return value.ToString("yyyyMMddHHmmssfff");
-        }
-
         public static void Update(Configuration config, bool forceDisable, PACServer pacSrv, bool noRetry = false)
         {
             bool global = config.global;
             bool enabled = config.enabled;
 
-            if (forceDisable)
+            if (forceDisable || WinINet.operational)
             {
                 enabled = false;
             }

shadowsocks-csharp/View/MenuViewController.cs

@@ -3,6 +3,7 @@ using Shadowsocks.Controller;
 using Shadowsocks.Model;
 using Shadowsocks.Properties;
 using Shadowsocks.Util;
+using Shadowsocks.Util.SystemProxy;
 using System;
 using System.Diagnostics;
 using System.Drawing;
@@ -38,7 +39,7 @@ namespace Shadowsocks.View
         private ToolStripMenuItem disableItem;
         private ToolStripMenuItem AutoStartupItem;
         private ToolStripMenuItem ShareOverLANItem;
-        private ToolStripSeparator  SeperatorItem;
+        private ToolStripSeparator SeperatorItem;
         private ToolStripMenuItem ConfigItem;
         private ToolStripMenuItem ServersItem;
         private ToolStripMenuItem globalModeItem;
@@ -504,7 +505,8 @@ namespace Shadowsocks.View
                     )
                 {
                     menuItem.Checked = true;
-                } else
+                }
+                else
                 {
                     menuItem.Checked = false;
                 }
@@ -668,6 +670,9 @@ namespace Shadowsocks.View
                 globalModeItem.Checked = config.global;
                 PACModeItem.Checked = !config.global;
             }
+
+            globalModeItem.Enabled = WinINet.operational;
+            PACModeItem.Enabled = WinINet.operational;
         }
 
         private void GlobalModeItem_Click(object sender, EventArgs e)