diff --git a/shadowsocks-csharp/Controller/Service/GfwListUpdater.cs b/shadowsocks-csharp/Controller/Service/GfwListUpdater.cs
index 344726aa..2497090d 100644
--- a/shadowsocks-csharp/Controller/Service/GfwListUpdater.cs
+++ b/shadowsocks-csharp/Controller/Service/GfwListUpdater.cs
@@ -16,12 +16,6 @@ namespace Shadowsocks.Controller
     {
         private const string GFWLIST_URL = "https://raw.githubusercontent.com/gfwlist/gfwlist/master/gfwlist.txt";
 
-        private static string PAC_FILE = PACServer.PAC_FILE;
-
-        private static string USER_RULE_FILE = PACServer.USER_RULE_FILE;
-
-        private static string USER_ABP_FILE = PACServer.USER_ABP_FILE;
-
         public event EventHandler<ResultEventArgs> UpdateCompleted;
 
         public event ErrorEventHandler Error;
@@ -42,9 +36,9 @@ namespace Shadowsocks.Controller
             {
                 File.WriteAllText(Utils.GetTempPath("gfwlist.txt"), e.Result, Encoding.UTF8);
                 List<string> lines = ParseResult(e.Result);
-                if (File.Exists(USER_RULE_FILE))
+                if (File.Exists(PACServer.USER_RULE_FILE))
                 {
-                    string local = File.ReadAllText(USER_RULE_FILE, Encoding.UTF8);
+                    string local = File.ReadAllText(PACServer.USER_RULE_FILE, Encoding.UTF8);
                     string[] rules = local.Split(new char[] { '\r', '\n' }, StringSplitOptions.RemoveEmptyEntries);
                     foreach (string rule in rules)
                     {
@@ -54,9 +48,9 @@ namespace Shadowsocks.Controller
                     }
                 }
                 string abpContent;
-                if (File.Exists(USER_ABP_FILE))
+                if (File.Exists(PACServer.USER_ABP_FILE))
                 {
-                    abpContent = File.ReadAllText(USER_ABP_FILE, Encoding.UTF8);
+                    abpContent = File.ReadAllText(PACServer.USER_ABP_FILE, Encoding.UTF8);
                 }
                 else
                 {
@@ -65,14 +59,14 @@ namespace Shadowsocks.Controller
                 abpContent = abpContent.Replace("__RULES__", JsonConvert.SerializeObject(lines, Formatting.Indented));
                 if (File.Exists(PACServer.PAC_FILE))
                 {
-                    string original = File.ReadAllText(PAC_FILE, Encoding.UTF8);
+                    string original = File.ReadAllText(PACServer.PAC_FILE, Encoding.UTF8);
                     if (original == abpContent)
                     {
                         UpdateCompleted(this, new ResultEventArgs(false));
                         return;
                     }
                 }
-                File.WriteAllText(PAC_FILE, abpContent, Encoding.UTF8);
+                File.WriteAllText(PACServer.PAC_FILE, abpContent, Encoding.UTF8);
                 if (UpdateCompleted != null)
                 {
                     UpdateCompleted(this, new ResultEventArgs(true));
diff --git a/shadowsocks-csharp/Controller/Service/PACServer.cs b/shadowsocks-csharp/Controller/Service/PACServer.cs
index ac8b762a..5db8b64a 100644
--- a/shadowsocks-csharp/Controller/Service/PACServer.cs
+++ b/shadowsocks-csharp/Controller/Service/PACServer.cs
@@ -1,23 +1,21 @@
-using Shadowsocks.Model;
-using Shadowsocks.Properties;
-using Shadowsocks.Util;
-using System;
+using System;
 using System.Collections;
-using System.Collections.Generic;
-using System.Diagnostics;
 using System.IO;
-using System.IO.Compression;
 using System.Net;
 using System.Net.Sockets;
 using System.Text;
 
+using Shadowsocks.Model;
+using Shadowsocks.Properties;
+using Shadowsocks.Util;
+
 namespace Shadowsocks.Controller
 {
     class PACServer : Listener.Service
     {
-        public static string PAC_FILE = "pac.txt";
-        public static string USER_RULE_FILE = "user-rule.txt";
-        public static string USER_ABP_FILE = "abp.txt";
+        public static readonly string PAC_FILE = "pac.txt";
+        public static readonly string USER_RULE_FILE = "user-rule.txt";
+        public static readonly string USER_ABP_FILE = "abp.txt";
 
         FileSystemWatcher PACFileWatcher;
         FileSystemWatcher UserRuleFileWatcher;
@@ -50,7 +48,7 @@ namespace Shadowsocks.Controller
                 bool hostMatch = false, pathMatch = false, useSocks = false;
                 foreach (string line in lines)
                 {
-                    string[] kv = line.Split(new char[]{':'}, 2);
+                    string[] kv = line.Split(new char[] { ':' }, 2);
                     if (kv.Length == 2)
                     {
                         if (kv[0] == "Host")
@@ -60,14 +58,14 @@ namespace Shadowsocks.Controller
                                 hostMatch = true;
                             }
                         }
-                        else if (kv[0] == "User-Agent")
-                        {
-                            // we need to drop connections when changing servers
-                            /* if (kv[1].IndexOf("Chrome") >= 0)
-                            {
-                                useSocks = true;
-                            } */
-                        }
+                        //else if (kv[0] == "User-Agent")
+                        //{
+                        //    // we need to drop connections when changing servers
+                        //    if (kv[1].IndexOf("Chrome") >= 0)
+                        //    {
+                        //        useSocks = true;
+                        //    }
+                        //}
                     }
                     else if (kv.Length == 1)
                     {
@@ -202,7 +200,6 @@ Connection: Close
         }
 
         #region FileSystemWatcher.OnChanged()
-
         // FileSystemWatcher Changed event is raised twice
         // http://stackoverflow.com/questions/1764809/filesystemwatcher-changed-event-is-raised-twice
         private static Hashtable fileChangedTime = new Hashtable();
@@ -221,7 +218,7 @@ Connection: Close
                     PACFileChanged(this, new EventArgs());
                 }
 
-                //lastly we update the last write time in the hashtable
+                // lastly we update the last write time in the hashtable
                 fileChangedTime[path] = currentLastWriteTime;
             }
         }
@@ -239,11 +236,10 @@ Connection: Close
                     Logging.Info($"Detected: User Rule file '{e.Name}' was {e.ChangeType.ToString().ToLower()}.");
                     UserRuleFileChanged(this, new EventArgs());
                 }
-                //lastly we update the last write time in the hashtable
+                // lastly we update the last write time in the hashtable
                 fileChangedTime[path] = currentLastWriteTime;
             }
         }
-
         #endregion
 
         private string GetPACAddress(byte[] requestBuf, int length, IPEndPoint localEndPoint, bool useSocks)