diff --git a/shadowsocks-csharp/Model/Configuration.cs b/shadowsocks-csharp/Model/Configuration.cs
index aa393c64..f712653e 100644
--- a/shadowsocks-csharp/Model/Configuration.cs
+++ b/shadowsocks-csharp/Model/Configuration.cs
@@ -11,7 +11,7 @@ namespace Shadowsocks.Model
     public class Configuration
     {
         [JsonIgnore]
-        private static Logger logger = LogManager.GetCurrentClassLogger();
+        private static readonly Logger logger = LogManager.GetCurrentClassLogger();
 
         public string version;
 
@@ -24,16 +24,10 @@ namespace Shadowsocks.Model
         public bool enabled;
         public bool shareOverLan;
         public bool isDefault;
-        // hidden
-        public bool isIPv6Enabled = false;
         public int localPort;
         public bool portableMode = true;
         public bool showPluginOutput;
         public string pacUrl;
-        // geosite config is hidden
-        public string geositeUrl;
-        public string geositeGroup = "geolocation-!cn";
-        public bool geositeBlacklistMode = true;
 
         public bool useOnlinePac;
         public bool secureLocalPac = true;
@@ -42,8 +36,13 @@ namespace Shadowsocks.Model
         public bool checkPreRelease;
         public bool isVerboseLogging;
 
-        // hidden config
-        public bool generateLegacyUrl = false;
+        // hidden options
+        public bool isIPv6Enabled = false; // for experimental ipv6 support
+        public bool generateLegacyUrl = false; // for pre-sip002 url compatibility
+        public string geositeUrl; // for custom geosite source (and rule group)
+        public string geositeGroup = "geolocation-!cn";
+        public bool geositeBlacklistMode = true;
+
 
         //public NLogConfig.LogLevel logLevel;
         public LogViewerConfig logViewer;
@@ -54,11 +53,10 @@ namespace Shadowsocks.Model
         NLogConfig nLogConfig;
 
         private static readonly string CONFIG_FILE = "gui-config.json";
-        private static readonly NLogConfig.LogLevel verboseLogLevel =
 #if DEBUG
-        NLogConfig.LogLevel.Trace;
+        private static readonly NLogConfig.LogLevel verboseLogLevel = NLogConfig.LogLevel.Trace;
 #else
-        NLogConfig.LogLevel.Debug;
+        private static readonly NLogConfig.LogLevel verboseLogLevel =  NLogConfig.LogLevel.Debug;
 #endif
 
 
@@ -200,9 +198,9 @@ namespace Shadowsocks.Model
                     sw.Flush();
                 }
                 try
-                {             
-                    // apply changs to NLog.config
-                    config.nLogConfig.SetLogLevel(config.isVerboseLogging? verboseLogLevel : NLogConfig.LogLevel.Info);
+                {
+                    // apply changes to NLog.config
+                    config.nLogConfig.SetLogLevel(config.isVerboseLogging ? verboseLogLevel : NLogConfig.LogLevel.Info);
                     NLogConfig.SaveXML(config.nLogConfig);
                 }
                 catch (Exception e)
@@ -218,7 +216,7 @@ namespace Shadowsocks.Model
 
         public static Server AddDefaultServerOrServer(Configuration config, Server server = null, int? index = null)
         {
-            if (config != null && config.configs != null)
+            if (config?.configs != null)
             {
                 server = (server ?? GetDefaultServer());
 
@@ -237,12 +235,6 @@ namespace Shadowsocks.Model
             return new Server();
         }
 
-        private static void Assert(bool condition)
-        {
-            if (!condition)
-                throw new Exception(I18N.GetString("assertion failure"));
-        }
-
         public static void CheckPort(int port)
         {
             if (port <= 0 || port > 65535)