diff --git a/appveyor.yml b/appveyor.yml
index 00a792d3..91340e8a 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,5 +1,5 @@
 version: 1.0.{build}
-image: Visual Studio 2015
+image: Visual Studio 2017
 environment:
   matrix:
     - platform: x86
diff --git a/shadowsocks-csharp/Controller/ShadowsocksController.cs b/shadowsocks-csharp/Controller/ShadowsocksController.cs
index b103c17a..70d5eb2f 100644
--- a/shadowsocks-csharp/Controller/ShadowsocksController.cs
+++ b/shadowsocks-csharp/Controller/ShadowsocksController.cs
@@ -2,21 +2,18 @@
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.IO;
+using System.Linq;
 using System.Net;
 using System.Net.Sockets;
 using System.Text;
 using System.Threading;
 using System.Web;
 using System.Windows.Forms;
-using Newtonsoft.Json;
 
+using Shadowsocks.Controller.Service;
 using Shadowsocks.Controller.Strategy;
 using Shadowsocks.Model;
-using Shadowsocks.Properties;
 using Shadowsocks.Util;
-using System.Linq;
-using Shadowsocks.Controller.Service;
-using Shadowsocks.Proxy;
 
 namespace Shadowsocks.Controller
 {
@@ -100,10 +97,7 @@ namespace Shadowsocks.Controller
 
         protected void ReportError(Exception e)
         {
-            if (Errored != null)
-            {
-                Errored(this, new ErrorEventArgs(e));
-            }
+            Errored?.Invoke(this, new ErrorEventArgs(e));
         }
 
         public Server GetCurrentServer()
@@ -132,7 +126,7 @@ namespace Shadowsocks.Controller
         {
             foreach (var strategy in _strategyManager.GetStrategies())
             {
-                if (strategy.ID == this._config.strategy)
+                if (strategy.ID == _config.strategy)
                 {
                     return strategy;
                 }
@@ -197,9 +191,13 @@ namespace Shadowsocks.Controller
         {
             try
             {
-                if (ssURL.IsNullOrEmpty() || ssURL.IsWhiteSpace()) return false;
+                if (ssURL.IsNullOrEmpty() || ssURL.IsWhiteSpace())
+                    return false;
+
                 var servers = Server.GetServers(ssURL);
-                if (servers == null || servers.Count == 0) return false;
+                if (servers == null || servers.Count == 0)
+                    return false;
+
                 foreach (var server in servers)
                 {
                     _config.configs.Add(server);
@@ -219,30 +217,24 @@ namespace Shadowsocks.Controller
         {
             _config.enabled = enabled;
             SaveConfig(_config);
-            if (EnableStatusChanged != null)
-            {
-                EnableStatusChanged(this, new EventArgs());
-            }
+
+            EnableStatusChanged?.Invoke(this, new EventArgs());
         }
 
         public void ToggleGlobal(bool global)
         {
             _config.global = global;
             SaveConfig(_config);
-            if (EnableGlobalChanged != null)
-            {
-                EnableGlobalChanged(this, new EventArgs());
-            }
+
+            EnableGlobalChanged?.Invoke(this, new EventArgs());
         }
 
         public void ToggleShareOverLAN(bool enabled)
         {
             _config.shareOverLan = enabled;
             SaveConfig(_config);
-            if (ShareOverLANStatusChanged != null)
-            {
-                ShareOverLANStatusChanged(this, new EventArgs());
-            }
+
+            ShareOverLANStatusChanged?.Invoke(this, new EventArgs());
         }
 
         public void SaveProxy(ProxyConfig proxyConfig)
@@ -255,10 +247,8 @@ namespace Shadowsocks.Controller
         {
             _config.isVerboseLogging = enabled;
             SaveConfig(_config);
-            if (VerboseLoggingStatusChanged != null)
-            {
-                VerboseLoggingStatusChanged(this, new EventArgs());
-            }
+
+            VerboseLoggingStatusChanged?.Invoke(this, new EventArgs());
         }
 
         public void SelectServerIndex(int index)
@@ -310,19 +300,15 @@ namespace Shadowsocks.Controller
         public void TouchPACFile()
         {
             string pacFilename = _pacServer.TouchPACFile();
-            if (PACFileReadyToOpen != null)
-            {
-                PACFileReadyToOpen(this, new PathEventArgs() { Path = pacFilename });
-            }
+
+            PACFileReadyToOpen?.Invoke(this, new PathEventArgs() { Path = pacFilename });
         }
 
         public void TouchUserRuleFile()
         {
             string userRuleFilename = _pacServer.TouchUserRuleFile();
-            if (UserRuleFileReadyToOpen != null)
-            {
-                UserRuleFileReadyToOpen(this, new PathEventArgs() { Path = userRuleFilename });
-            }
+
+            UserRuleFileReadyToOpen?.Invoke(this, new PathEventArgs() { Path = userRuleFilename });
         }
 
         public string GetServerURLForCurrentServer()
@@ -381,60 +367,51 @@ namespace Shadowsocks.Controller
 
         public void UpdateStatisticsConfiguration(bool enabled)
         {
-            if (availabilityStatistics == null) return;
-            availabilityStatistics.UpdateConfiguration(this);
-            _config.availabilityStatistics = enabled;
-            SaveConfig(_config);
+            if (availabilityStatistics != null)
+            {
+                availabilityStatistics.UpdateConfiguration(this);
+                _config.availabilityStatistics = enabled;
+                SaveConfig(_config);
+            }
         }
 
         public void SavePACUrl(string pacUrl)
         {
             _config.pacUrl = pacUrl;
             SaveConfig(_config);
-            if (ConfigChanged != null)
-            {
-                ConfigChanged(this, new EventArgs());
-            }
+
+            ConfigChanged?.Invoke(this, new EventArgs());
         }
 
         public void UseOnlinePAC(bool useOnlinePac)
         {
             _config.useOnlinePac = useOnlinePac;
             SaveConfig(_config);
-            if (ConfigChanged != null)
-            {
-                ConfigChanged(this, new EventArgs());
-            }
+
+            ConfigChanged?.Invoke(this, new EventArgs());
         }
 
         public void ToggleSecureLocalPac(bool enabled)
         {
             _config.secureLocalPac = enabled;
             SaveConfig(_config);
-            if (ConfigChanged != null)
-            {
-                ConfigChanged(this, new EventArgs());
-            }
+
+            ConfigChanged?.Invoke(this, new EventArgs());
         }
 
         public void ToggleCheckingUpdate(bool enabled)
         {
             _config.autoCheckUpdate = enabled;
             Configuration.Save(_config);
-            if (ConfigChanged != null)
-            {
-                ConfigChanged(this, new EventArgs());
-            }
+
+            ConfigChanged?.Invoke(this, new EventArgs());
         }
 
         public void ToggleCheckingPreRelease(bool enabled)
         {
             _config.checkPreRelease = enabled;
             Configuration.Save(_config);
-            if (ConfigChanged != null)
-            {
-                ConfigChanged(this, new EventArgs());
-            }
+            ConfigChanged?.Invoke(this, new EventArgs());
         }
 
         public void SaveLogViewerConfig(LogViewerConfig newConfig)
@@ -442,20 +419,16 @@ namespace Shadowsocks.Controller
             _config.logViewer = newConfig;
             newConfig.SaveSize();
             Configuration.Save(_config);
-            if (ConfigChanged != null)
-            {
-                ConfigChanged(this, new EventArgs());
-            }
+
+            ConfigChanged?.Invoke(this, new EventArgs());
         }
 
         public void SaveHotkeyConfig(HotkeyConfig newConfig)
         {
             _config.hotkey = newConfig;
             SaveConfig(_config);
-            if (ConfigChanged != null)
-            {
-                ConfigChanged(this, new EventArgs());
-            }
+
+            ConfigChanged?.Invoke(this, new EventArgs());
         }
 
         public void UpdateLatency(Server server, TimeSpan latency)
@@ -498,15 +471,15 @@ namespace Shadowsocks.Controller
             if (_pacServer == null)
             {
                 _pacServer = new PACServer();
-                _pacServer.PACFileChanged += pacServer_PACFileChanged;
-                _pacServer.UserRuleFileChanged += pacServer_UserRuleFileChanged;
+                _pacServer.PACFileChanged += PacServer_PACFileChanged;
+                _pacServer.UserRuleFileChanged += PacServer_UserRuleFileChanged;
             }
             _pacServer.UpdateConfiguration(_config);
             if (gfwListUpdater == null)
             {
                 gfwListUpdater = new GFWListUpdater();
-                gfwListUpdater.UpdateCompleted += pacServer_PACUpdateCompleted;
-                gfwListUpdater.Error += pacServer_PACUpdateError;
+                gfwListUpdater.UpdateCompleted += PacServer_PACUpdateCompleted;
+                gfwListUpdater.Error += PacServer_PACUpdateError;
             }
 
             availabilityStatistics.UpdateConfiguration(this);
@@ -536,11 +509,13 @@ namespace Shadowsocks.Controller
 
                 TCPRelay tcpRelay = new TCPRelay(this, _config);
                 UDPRelay udpRelay = new UDPRelay(this);
-                List<Listener.IService> services = new List<Listener.IService>();
-                services.Add(tcpRelay);
-                services.Add(udpRelay);
-                services.Add(_pacServer);
-                services.Add(new PortForwarder(privoxyRunner.RunningPort));
+                List<Listener.IService> services = new List<Listener.IService>
+                {
+                    tcpRelay,
+                    udpRelay,
+                    _pacServer,
+                    new PortForwarder(privoxyRunner.RunningPort)
+                };
                 _listener = new Listener(services);
                 _listener.Start(_config);
             }
@@ -548,9 +523,8 @@ namespace Shadowsocks.Controller
             {
                 // translate Microsoft language into human language
                 // i.e. An attempt was made to access a socket in a way forbidden by its access permissions => Port already in use
-                if (e is SocketException)
+                if (e is SocketException se)
                 {
-                    SocketException se = (SocketException)e;
                     if (se.SocketErrorCode == SocketError.AddressAlreadyInUse)
                     {
                         e = new Exception(I18N.GetString("Port {0} already in use", _config.localPort), e);
@@ -564,10 +538,7 @@ namespace Shadowsocks.Controller
                 ReportError(e);
             }
 
-            if (ConfigChanged != null)
-            {
-                ConfigChanged(this, new EventArgs());
-            }
+            ConfigChanged?.Invoke(this, new EventArgs());
 
             UpdateSystemProxy();
             Utils.ReleaseMemory(true);
@@ -590,25 +561,23 @@ namespace Shadowsocks.Controller
             SystemProxy.Update(_config, false, _pacServer);
         }
 
-        private void pacServer_PACFileChanged(object sender, EventArgs e)
+        private void PacServer_PACFileChanged(object sender, EventArgs e)
         {
             UpdateSystemProxy();
         }
 
-        private void pacServer_PACUpdateCompleted(object sender, GFWListUpdater.ResultEventArgs e)
+        private void PacServer_PACUpdateCompleted(object sender, GFWListUpdater.ResultEventArgs e)
         {
-            if (UpdatePACFromGFWListCompleted != null)
-                UpdatePACFromGFWListCompleted(this, e);
+            UpdatePACFromGFWListCompleted?.Invoke(this, e);
         }
 
-        private void pacServer_PACUpdateError(object sender, ErrorEventArgs e)
+        private void PacServer_PACUpdateError(object sender, ErrorEventArgs e)
         {
-            if (UpdatePACFromGFWListError != null)
-                UpdatePACFromGFWListError(this, e);
+            UpdatePACFromGFWListError?.Invoke(this, e);
         }
 
         private static readonly IEnumerable<char> IgnoredLineBegins = new[] { '!', '[' };
-        private void pacServer_UserRuleFileChanged(object sender, EventArgs e)
+        private void PacServer_UserRuleFileChanged(object sender, EventArgs e)
         {
             if (!File.Exists(Utils.GetTempPath("gfwlist.txt")))
             {
@@ -630,8 +599,10 @@ namespace Shadowsocks.Controller
 
         private void StartReleasingMemory()
         {
-            _ramThread = new Thread(new ThreadStart(ReleaseMemory));
-            _ramThread.IsBackground = true;
+            _ramThread = new Thread(new ThreadStart(ReleaseMemory))
+            {
+                IsBackground = true
+            };
             _ramThread.Start();
         }
 
@@ -655,8 +626,10 @@ namespace Shadowsocks.Controller
             {
                 trafficPerSecondQueue.Enqueue(new TrafficPerSecond());
             }
-            _trafficThread = new Thread(new ThreadStart(() => TrafficStatistics(queueMaxSize)));
-            _trafficThread.IsBackground = true;
+            _trafficThread = new Thread(new ThreadStart(() => TrafficStatistics(queueMaxSize)))
+            {
+                IsBackground = true
+            };
             _trafficThread.Start();
         }
 
@@ -666,10 +639,11 @@ namespace Shadowsocks.Controller
             while (true)
             {
                 previous = trafficPerSecondQueue.Last();
-                current = new TrafficPerSecond();
-
-                current.inboundCounter = InboundCounter;
-                current.outboundCounter = OutboundCounter;
+                current = new TrafficPerSecond
+                {
+                    inboundCounter = InboundCounter,
+                    outboundCounter = OutboundCounter
+                };
                 current.inboundIncreasement = current.inboundCounter - previous.inboundCounter;
                 current.outboundIncreasement = current.outboundCounter - previous.outboundCounter;
 
diff --git a/shadowsocks-csharp/Data/ja.txt b/shadowsocks-csharp/Data/ja.txt
index 690e0d58..3b60941c 100644
--- a/shadowsocks-csharp/Data/ja.txt
+++ b/shadowsocks-csharp/Data/ja.txt
@@ -122,7 +122,6 @@ Port {0} is reserved by system= ポート番号 {0} はシステムによって
 Invalid server address=サーバーアドレスが無効です。
 Illegal port number format=ポート番号のフォーマットが無効です。
 Illegal timeout format=タイムアウト値のフォーマットが無効です。
-Please add at least one server=少なくとも一つのサーバーを指定して下さい。
 Server IP can not be blank=サーバー IP が指定されていません。
 Password can not be blank=パスワードが指定されていません。
 Port out of range=ポート番号は範囲外です。
diff --git a/shadowsocks-csharp/Data/zh_CN.txt b/shadowsocks-csharp/Data/zh_CN.txt
index b26593b0..d89385ea 100644
--- a/shadowsocks-csharp/Data/zh_CN.txt
+++ b/shadowsocks-csharp/Data/zh_CN.txt
@@ -123,7 +123,6 @@ Port {0} is reserved by system=端口 {0} 是系统保留端口
 Invalid server address=非法服务器地址
 Illegal port number format=非法端口格式
 Illegal timeout format=非法超时格式
-Please add at least one server=请添加至少一个服务器
 Server IP can not be blank=服务器 IP 不能为空
 Password can not be blank=密码不能为空
 Port out of range=端口超出范围
@@ -155,6 +154,14 @@ Register hotkey failed=注册快捷键失败
 Cannot parse hotkey: {0}=解析快捷键失败: {0}
 Timeout is invalid, it should not exceed {0}=超时无效，不应超过 {0}
 
+Operation failure=操作失败
+Auto save failed=自动保存失败
+Whether to discard unconfigured servers=是否丢弃未配置的服务器
+Invalid server address, Cannot automatically save or discard changes=非法服务器地址，无法自动保存是否丢弃修改
+Illegal port number format, Cannot automatically save or discard changes=非法端口格式，无法自动保存是否丢弃修改
+Password can not be blank, Cannot automatically save or discard changes=密码不能为空，无法自动保存是否丢弃修改
+Illegal timeout format, Cannot automatically save or discard changes=非法超时格式，无法自动保存是否丢弃修改
+
 Error occured when process proxy setting, do you want reset current setting and retry?=处理代理设置时发生错误，是否重置当前代理设置并重试？
 Unrecoverable proxy setting error occured, see log for detail=发生不可恢复的代理设置错误，查看日志以取得详情
 Auth user can not be blank=认证用户不能为空
diff --git a/shadowsocks-csharp/Data/zh_TW.txt b/shadowsocks-csharp/Data/zh_TW.txt
index d4b75ef8..5c2c19c5 100644
--- a/shadowsocks-csharp/Data/zh_TW.txt
+++ b/shadowsocks-csharp/Data/zh_TW.txt
@@ -122,7 +122,6 @@ Port {0} is reserved by system=連接埠號碼 {0} 由系統保留
 Invalid server address=無效伺服器位址
 Illegal port number format=無效連接埠號碼格式
 Illegal timeout format=無效逾時格式
-Please add at least one server=請新增至少一個伺服器
 Server IP can not be blank=伺服器 IP 不能為空
 Password can not be blank=密碼不能為空
 Port out of range=連接埠號碼超出範圍
diff --git a/shadowsocks-csharp/Model/Configuration.cs b/shadowsocks-csharp/Model/Configuration.cs
index 4d26b72f..3bb1af3b 100644
--- a/shadowsocks-csharp/Model/Configuration.cs
+++ b/shadowsocks-csharp/Model/Configuration.cs
@@ -1,9 +1,8 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
-
-using Shadowsocks.Controller;
 using Newtonsoft.Json;
+using Shadowsocks.Controller;
 
 namespace Shadowsocks.Model
 {
@@ -34,7 +33,7 @@ namespace Shadowsocks.Model
         public ProxyConfig proxy;
         public HotkeyConfig hotkey;
 
-        private static string CONFIG_FILE = "gui-config.json";
+        private static readonly string CONFIG_FILE = "gui-config.json";
 
         public Server GetCurrentServer()
         {
@@ -46,12 +45,25 @@ namespace Shadowsocks.Model
 
         public static void CheckServer(Server server)
         {
+            CheckServer(server.server);
             CheckPort(server.server_port);
             CheckPassword(server.password);
-            CheckServer(server.server);
             CheckTimeout(server.timeout, Server.MaxServerTimeoutSec);
         }
 
+        public static bool ChecksServer(Server server)
+        {
+            try
+            {
+                CheckServer(server);
+                return true;
+            }
+            catch (Exception)
+            {
+                return false;
+            }
+        }
+
         public static Configuration Load()
         {
             try
@@ -125,12 +137,18 @@ namespace Shadowsocks.Model
             }
         }
 
-        public static Server AddDefaultServerOrServer(Configuration config, Server server = null)
+        public static Server AddDefaultServerOrServer(Configuration config, Server server = null, int? index = null)
         {
             if (config != null && config.configs != null)
             {
                 server = (server ?? GetDefaultServer());
-                config.configs.Add(server);
+
+                config.configs.Insert(index.GetValueOrDefault(config.configs.Count), server);
+
+                //if (index.HasValue)
+                //    config.configs.Insert(index.Value, server);
+                //else
+                //    config.configs.Add(server);
             }
             return server;
         }
@@ -174,8 +192,7 @@ namespace Shadowsocks.Model
         public static void CheckTimeout(int timeout, int maxTimeout)
         {
             if (timeout <= 0 || timeout > maxTimeout)
-                throw new ArgumentException(
-                    I18N.GetString("Timeout is invalid, it should not exceed {0}", maxTimeout));
+                throw new ArgumentException(I18N.GetString("Timeout is invalid, it should not exceed {0}", maxTimeout));
         }
 
         public static void CheckProxyAuthUser(string user)
diff --git a/shadowsocks-csharp/View/ConfigForm.cs b/shadowsocks-csharp/View/ConfigForm.cs
index 2716e931..963a5d4a 100755
--- a/shadowsocks-csharp/View/ConfigForm.cs
+++ b/shadowsocks-csharp/View/ConfigForm.cs
@@ -1,5 +1,6 @@
 using System;
 using System.Drawing;
+using System.Runtime.CompilerServices;
 using System.Windows.Forms;
 using Shadowsocks.Controller;
 using Shadowsocks.Model;
@@ -17,20 +18,20 @@ namespace Shadowsocks.View
 
         public ConfigForm(ShadowsocksController controller)
         {
-            this.Font = SystemFonts.MessageBoxFont;
+            Font = SystemFonts.MessageBoxFont;
             InitializeComponent();
 
             // a dirty hack
-            this.ServersListBox.Dock = DockStyle.Fill;
-            this.tableLayoutPanel5.Dock = DockStyle.Fill;
-            this.PerformLayout();
+            ServersListBox.Dock = DockStyle.Fill;
+            tableLayoutPanel5.Dock = DockStyle.Fill;
+            PerformLayout();
 
             UpdateTexts();
             SetupValueChangedListeners();
-            this.Icon = Icon.FromHandle(Resources.ssw128.GetHicon());
+            Icon = Icon.FromHandle(Resources.ssw128.GetHicon());
 
             this.controller = controller;
-            controller.ConfigChanged += controller_ConfigChanged;
+            controller.ConfigChanged += Controller_ConfigChanged;
 
             LoadCurrentConfiguration();
         }
@@ -51,7 +52,7 @@ namespace Shadowsocks.View
             NeedPluginArgCheckBox.Text = I18N.GetString("Need Plugin Argument");
             ProxyPortLabel.Text = I18N.GetString("Proxy Port");
             PortableModeCheckBox.Text = I18N.GetString("Portable Mode");
-            toolTip1.SetToolTip(this.PortableModeCheckBox, I18N.GetString("Restart required"));
+            toolTip1.SetToolTip(PortableModeCheckBox, I18N.GetString("Restart required"));
             RemarksLabel.Text = I18N.GetString("Remarks");
             TimeoutLabel.Text = I18N.GetString("Timeout(Sec)");
             ServerGroupBox.Text = I18N.GetString("Server");
@@ -60,7 +61,7 @@ namespace Shadowsocks.View
             ApplyButton.Text = I18N.GetString("Apply");
             MoveUpButton.Text = I18N.GetString("Move &Up");
             MoveDownButton.Text = I18N.GetString("Move D&own");
-            this.Text = I18N.GetString("Edit Servers");
+            Text = I18N.GetString("Edit Servers");
         }
 
         private void SetupValueChangedListeners()
@@ -78,7 +79,7 @@ namespace Shadowsocks.View
             ServerPortTextBox.TextChanged += ConfigValueChanged;
         }
 
-        private void controller_ConfigChanged(object sender, EventArgs e)
+        private void Controller_ConfigChanged(object sender, EventArgs e)
         {
             LoadCurrentConfiguration();
         }
@@ -88,7 +89,13 @@ namespace Shadowsocks.View
             ApplyButton.Enabled = true;
         }
 
-        private bool ValidateAndSaveSelectedServerDetails()
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private void UpdateIndexToEnd()
+        {
+            _lastSelectedIndex = (ServersListBox.SelectedIndex = (_modifiedConfiguration.configs.Count - 1));
+        }
+
+        private bool ValidateAndSaveSelectedServerDetails(bool isSave = false, bool isCopy = false)
         {
             try
             {
@@ -96,15 +103,17 @@ namespace Shadowsocks.View
                 {
                     return true;
                 }
-                Server server = GetServerDetailsFromUI();
-                if (server == null)
+
+                bool verify = GetServerDetailsFromUI(out Server server, isSave, isCopy);
+
+                if (server != null)
                 {
-                    return false;
-                }
-                Configuration.CheckServer(server);
-                _modifiedConfiguration.configs[_lastSelectedIndex] = server;
+                    if (isSave || isCopy)
+                        Configuration.CheckServer(server);
 
-                return true;
+                    _modifiedConfiguration.configs[_lastSelectedIndex] = server;
+                }
+                return verify;
             }
             catch (Exception ex)
             {
@@ -113,36 +122,209 @@ namespace Shadowsocks.View
             return false;
         }
 
-        private Server GetServerDetailsFromUI()
+        private bool GetServerDetailsFromUI(out Server server, bool isSave = false, bool isCopy = false)
+        {
+            server = null;
+
+            bool? checkIP = false;
+            bool? checkPort = false;
+            bool? checkPassword = false;
+            bool? checkTimeout = false;
+
+            if ((checkIP = CheckIPTextBox(out string address, isSave, isCopy)).GetValueOrDefault(false) && address != null
+                    && (checkPort = CheckServerPortTextBox(out int? addressPort, isSave, isCopy)).GetValueOrDefault(false) && addressPort.HasValue
+                        && (checkPassword = CheckPasswordTextBox(out string serverPassword, isSave, isCopy)).GetValueOrDefault(false) && serverPassword != null
+                            && (checkTimeout = CheckTimeoutTextBox(out int? timeout, isSave, isCopy)).GetValueOrDefault(false) && timeout.HasValue)
+            {
+                server = new Server()
+                {
+                    server = address,
+                    server_port = addressPort.Value,
+                    password = serverPassword,
+                    method = EncryptionSelect.Text,
+                    plugin = PluginTextBox.Text,
+                    plugin_opts = PluginOptionsTextBox.Text,
+                    plugin_args = PluginArgumentsTextBox.Text,
+                    remarks = RemarksTextBox.Text,
+                    timeout = timeout.Value,
+                };
+
+                return true;
+            }
+
+            if (checkIP == null || checkPort == null || checkTimeout == null)
+            {
+                _modifiedConfiguration.configs.RemoveAt(_lastSelectedIndex);
+                ServersListBox.SelectedIndexChanged -= ServersListBox_SelectedIndexChanged;
+
+                LoadServerNameListToUI(_modifiedConfiguration);
+                UpdateIndexToEnd();
+
+                ServersListBox.SelectedIndexChanged += ServersListBox_SelectedIndexChanged;
+                return true;
+            }
+            else
+                return false;
+        }
+
+        #region GetServerDetailsFromUI Check
+
+        private bool? CheckIPTextBox(out string address, bool isSave, bool isCopy)
+        {
+            address = null;
+            string outAddress;
+            if (Uri.CheckHostName(outAddress = IPTextBox.Text.Trim()) == UriHostNameType.Unknown)
+            {
+                if (!isSave && !isCopy && ServersListBox.Items.Count > 1 && I18N.GetString("New server").Equals(ServersListBox.Items[_lastSelectedIndex].ToString()))
+                {
+                    DialogResult result = MessageBox.Show(I18N.GetString("Whether to discard unconfigured servers"), I18N.GetString("Operation failure"), MessageBoxButtons.OKCancel);
+
+                    if (result == DialogResult.OK)
+                        return null;
+                }
+                else if (ApplyButton.Enabled && !isSave && !isCopy)
+                {
+                    var result = MessageBox.Show(I18N.GetString("Invalid server address, Cannot automatically save or discard changes"), I18N.GetString("Auto save failed"), MessageBoxButtons.OKCancel);
+
+                    if (result == DialogResult.Cancel)
+                        return false;
+                    else
+                    {
+                        address = _modifiedConfiguration.configs[_lastSelectedIndex].server;
+                        return true;
+                    }
+                }
+                else
+                {
+                    MessageBox.Show(I18N.GetString("Invalid server address"), I18N.GetString("Operation failure"));
+                    IPTextBox.Focus();
+                }
+                return false;
+            }
+            else
+            {
+                address = outAddress;
+            }
+            return true;
+        }
+
+        private bool? CheckServerPortTextBox(out int? addressPort, bool isSave, bool isCopy)
+        {
+            addressPort = null;
+            if (!int.TryParse(ServerPortTextBox.Text, out int outaddressPort))
+            {
+                if (!isSave && !isCopy && ServersListBox.Items.Count > 1 && I18N.GetString("New server").Equals(ServersListBox.Items[_lastSelectedIndex].ToString()))
+                {
+                    DialogResult result = MessageBox.Show(I18N.GetString("Whether to discard unconfigured servers"), I18N.GetString("Operation failure"), MessageBoxButtons.OKCancel);
+
+                    if (result == DialogResult.OK)
+                        return null;
+                }
+                else if (!isSave && !isCopy)
+                {
+                    var result = MessageBox.Show(I18N.GetString("Illegal port number format, Cannot automatically save or discard changes"), I18N.GetString("Auto save failed"), MessageBoxButtons.OKCancel);
+
+                    if (result == DialogResult.Cancel)
+                        return false;
+                    else
+                    {
+                        addressPort = _modifiedConfiguration.configs[_lastSelectedIndex].server_port;
+                        return true;
+                    }
+                }
+                else
+                {
+                    MessageBox.Show(I18N.GetString("Illegal port number format"), I18N.GetString("Operation failure"));
+                    ServerPortTextBox.Focus();
+                }
+                return false;
+            }
+            else
+            {
+                addressPort = outaddressPort;
+            }
+            return true;
+        }
+
+        private bool? CheckPasswordTextBox(out string password, bool isSave, bool isCopy)
         {
-            Server server = new Server();
-            if (Uri.CheckHostName(server.server = IPTextBox.Text.Trim()) == UriHostNameType.Unknown)
+            password = null;
+            string outPassword;
+            if ((outPassword = PasswordTextBox.Text).IsNullOrWhiteSpace())
             {
-                MessageBox.Show(I18N.GetString("Invalid server address"));
-                IPTextBox.Focus();
-                return null;
+                if (!isSave && !isCopy && ServersListBox.Items.Count > 1 && I18N.GetString("New server").Equals(ServersListBox.Items[_lastSelectedIndex].ToString()))
+                {
+                    DialogResult result = MessageBox.Show(I18N.GetString("Whether to discard unconfigured servers"), I18N.GetString("Operation failure"), MessageBoxButtons.OKCancel);
+
+                    if (result == DialogResult.OK)
+                        return null;
+                }
+                else if (ApplyButton.Enabled && !isSave && !isCopy)
+                {
+                    var result = MessageBox.Show(I18N.GetString("Password can not be blank, Cannot automatically save or discard changes"), I18N.GetString("Auto save failed"), MessageBoxButtons.OKCancel);
+
+                    if (result == DialogResult.Cancel)
+                        return false;
+                    else
+                    {
+                        password = _modifiedConfiguration.configs[_lastSelectedIndex].password;
+                        return true;
+                    }
+                }
+                else
+                {
+                    MessageBox.Show(I18N.GetString("Password can not be blank"), I18N.GetString("Operation failure"));
+                    PasswordTextBox.Focus();
+                }
+                return false;
             }
-            if (!int.TryParse(ServerPortTextBox.Text, out server.server_port))
+            else
             {
-                MessageBox.Show(I18N.GetString("Illegal port number format"));
-                ServerPortTextBox.Focus();
-                return null;
+                password = outPassword;
             }
-            server.password = PasswordTextBox.Text;
-            server.method = EncryptionSelect.Text;
-            server.plugin = PluginTextBox.Text;
-            server.plugin_opts = PluginOptionsTextBox.Text;
-            server.plugin_args = PluginArgumentsTextBox.Text;
-            server.remarks = RemarksTextBox.Text;
-            if (!int.TryParse(TimeoutTextBox.Text, out server.timeout))
+            return true;
+        }
+
+        private bool? CheckTimeoutTextBox(out int? timeout, bool isSave, bool isCopy)
+        {
+            timeout = null;
+            if (!int.TryParse(TimeoutTextBox.Text, out int outTimeout))
+            {
+                if (!isSave && !isCopy && ServersListBox.Items.Count > 1 && I18N.GetString("New server").Equals(ServersListBox.Items[_lastSelectedIndex].ToString()))
+                {
+                    DialogResult result = MessageBox.Show(I18N.GetString("Whether to discard unconfigured servers"), I18N.GetString("Operation failure"), MessageBoxButtons.OKCancel);
+
+                    if (result == DialogResult.OK)
+                        return null;
+                }
+                else if (ApplyButton.Enabled && !isSave && !isCopy)
+                {
+                    var result = MessageBox.Show(I18N.GetString("Illegal timeout format, Cannot automatically save or discard changes"), I18N.GetString("Auto save failed"), MessageBoxButtons.OKCancel);
+
+                    if (result == DialogResult.Cancel)
+                        return false;
+                    else
+                    {
+                        timeout = _modifiedConfiguration.configs[_lastSelectedIndex].timeout;
+                        return true;
+                    }
+                }
+                else
+                {
+                    MessageBox.Show(I18N.GetString("Illegal timeout format"), I18N.GetString("Operation failure"));
+                    TimeoutTextBox.Focus();
+                }
+                return false;
+            }
+            else
             {
-                MessageBox.Show(I18N.GetString("Illegal timeout format"));
-                TimeoutTextBox.Focus();
-                return null;
+                timeout = outTimeout;
             }
-            return server;
+            return true;
         }
 
+        #endregion
+
         private void LoadSelectedServerDetails()
         {
             if (ServersListBox.SelectedIndex >= 0 && ServersListBox.SelectedIndex < _modifiedConfiguration.configs.Count)
@@ -168,6 +350,8 @@ namespace Shadowsocks.View
 
             RemarksTextBox.Text = server.remarks;
             TimeoutTextBox.Text = server.timeout.ToString();
+
+            ApplyButton.Enabled = false;
         }
 
         private void ShowHidePluginArgInput(bool show)
@@ -176,7 +360,6 @@ namespace Shadowsocks.View
             PluginArgumentsLabel.Visible = show;
         }
 
-
         private void LoadServerNameListToUI(Configuration configuration)
         {
             ServersListBox.Items.Clear();
@@ -200,20 +383,17 @@ namespace Shadowsocks.View
             ServersListBox.SelectedIndex = _lastSelectedIndex;
             UpdateButtons();
             LoadSelectedServerDetails();
+
             ProxyPortTextBox.Text = _modifiedConfiguration.localPort.ToString();
             PortableModeCheckBox.Checked = _modifiedConfiguration.portableMode;
+
             ApplyButton.Enabled = false;
         }
 
         private bool SaveValidConfiguration()
         {
-            if (!ValidateAndSaveSelectedServerDetails())
-            {
-                return false;
-            }
-            if (_modifiedConfiguration.configs.Count == 0)
+            if (!ValidateAndSaveSelectedServerDetails(isSave: true))
             {
-                MessageBox.Show(I18N.GetString("Please add at least one server"));
                 return false;
             }
 
@@ -269,81 +449,62 @@ namespace Shadowsocks.View
 
         private void AddButton_Click(object sender, EventArgs e)
         {
-            if (!ValidateAndSaveSelectedServerDetails())
+            if (ValidateAndSaveSelectedServerDetails(isSave: true))
             {
-                return;
+                Configuration.AddDefaultServerOrServer(_modifiedConfiguration);
+                LoadServerNameListToUI(_modifiedConfiguration);
+                UpdateIndexToEnd();
             }
-            Configuration.AddDefaultServerOrServer(_modifiedConfiguration);
-            LoadServerNameListToUI(_modifiedConfiguration);
-            ServersListBox.SelectedIndex = _modifiedConfiguration.configs.Count - 1;
-            _lastSelectedIndex = ServersListBox.SelectedIndex;
         }
 
         private void DuplicateButton_Click(object sender, EventArgs e)
         {
-            if (_lastSelectedIndex == -1 || _lastSelectedIndex > _modifiedConfiguration.configs.Count
-                || !ValidateAndSaveSelectedServerDetails())
+            if (ValidateAndSaveSelectedServerDetails(isCopy: true))
             {
-                return;
+                Server currServer = _modifiedConfiguration.configs[_lastSelectedIndex];
+                Configuration.AddDefaultServerOrServer(_modifiedConfiguration, currServer);
+                LoadServerNameListToUI(_modifiedConfiguration);
+                UpdateIndexToEnd();
             }
-            Server currServer = _modifiedConfiguration.configs[_lastSelectedIndex];
-            var currIndex = _modifiedConfiguration.configs.IndexOf(currServer);
-            _modifiedConfiguration.configs.Insert(currIndex + 1, currServer);
-            LoadServerNameListToUI(_modifiedConfiguration);
-            ServersListBox.SelectedIndex = currIndex + 1;
-            _lastSelectedIndex = ServersListBox.SelectedIndex;
         }
 
         private void DeleteButton_Click(object sender, EventArgs e)
         {
-            _lastSelectedIndex = ServersListBox.SelectedIndex;
-            if (_lastSelectedIndex >= 0 && _lastSelectedIndex < _modifiedConfiguration.configs.Count)
-            {
-                _modifiedConfiguration.configs.RemoveAt(_lastSelectedIndex);
-            }
+            _modifiedConfiguration.configs.RemoveAt(_lastSelectedIndex);
+
             if (_modifiedConfiguration.configs.Count == 0)
             {
                 Configuration.AddDefaultServerOrServer(_modifiedConfiguration);
             }
-            if (_lastSelectedIndex >= _modifiedConfiguration.configs.Count)
-            {
-                // can be -1
-                _lastSelectedIndex = _modifiedConfiguration.configs.Count - 1;
-            }
-            ServersListBox.SelectedIndex = _lastSelectedIndex;
+
             LoadServerNameListToUI(_modifiedConfiguration);
-            ServersListBox.SelectedIndex = _lastSelectedIndex;
+            UpdateIndexToEnd();
             LoadSelectedServerDetails();
 
             UpdateButtons();
         }
 
-        private void OKButton_Click(object sender, EventArgs e)
-        {
-            if (SaveValidConfiguration())
-            {
-                this.Close();
-            }
-        }
-
-        private void CancelButton_Click(object sender, EventArgs e)
-        {
-            this.Close();
-        }
-
-        private void ApplyButton_Click(object sender, EventArgs e)
+        private void UpdateButtons()
         {
-            SaveValidConfiguration();
+            DeleteButton.Enabled = (ServersListBox.Items.Count > 0);
+            MoveUpButton.Enabled = (ServersListBox.SelectedIndex > 0);
+            MoveDownButton.Enabled = (ServersListBox.SelectedIndex < ServersListBox.Items.Count - 1);
         }
 
-        private void ConfigForm_Shown(object sender, EventArgs e)
+        private void MoveUpButton_Click(object sender, EventArgs e)
         {
-            IPTextBox.Focus();
+            if (ServersListBox.SelectedIndex > 0)
+            {
+                MoveConfigItem(-1);  // -1 means move backward
+            }
         }
 
-        private void ConfigForm_FormClosed(object sender, FormClosedEventArgs e)
+        private void MoveDownButton_Click(object sender, EventArgs e)
         {
-            controller.ConfigChanged -= controller_ConfigChanged;
+            if (ServersListBox.SelectedIndex < ServersListBox.Items.Count - 1)
+            {
+                MoveConfigItem(+1);  // +1 means move forward
+            }
         }
 
         private void MoveConfigItem(int step)
@@ -368,45 +529,42 @@ namespace Shadowsocks.View
             UpdateButtons();
         }
 
-        private void UpdateButtons()
+        private void OKButton_Click(object sender, EventArgs e)
         {
-            DeleteButton.Enabled = (ServersListBox.Items.Count > 0);
-            MoveUpButton.Enabled = (ServersListBox.SelectedIndex > 0);
-            MoveDownButton.Enabled = (ServersListBox.SelectedIndex < ServersListBox.Items.Count - 1);
+            if (SaveValidConfiguration())
+            {
+                Close();
+            }
         }
 
-        private void MoveUpButton_Click(object sender, EventArgs e)
+        private void CancelButton_Click(object sender, EventArgs e)
         {
-            if (!ValidateAndSaveSelectedServerDetails())
-            {
-                return;
-            }
-            if (ServersListBox.SelectedIndex > 0)
-            {
-                MoveConfigItem(-1);  // -1 means move backward
-            }
+            Close();
         }
 
-        private void MoveDownButton_Click(object sender, EventArgs e)
+        private void ApplyButton_Click(object sender, EventArgs e)
         {
-            if (!ValidateAndSaveSelectedServerDetails())
-            {
-                return;
-            }
-            if (ServersListBox.SelectedIndex < ServersListBox.Items.Count - 1)
-            {
-                MoveConfigItem(+1);  // +1 means move forward
-            }
+            SaveValidConfiguration();
+        }
+
+        private void ConfigForm_Shown(object sender, EventArgs e)
+        {
+            IPTextBox.Focus();
+        }
+
+        private void ConfigForm_FormClosed(object sender, FormClosedEventArgs e)
+        {
+            controller.ConfigChanged -= Controller_ConfigChanged;
         }
 
         private void ShowPasswdCheckBox_CheckedChanged(object sender, EventArgs e)
         {
-            this.PasswordTextBox.UseSystemPasswordChar = !this.ShowPasswdCheckBox.Checked;
+            PasswordTextBox.UseSystemPasswordChar = !ShowPasswdCheckBox.Checked;
         }
 
         private void UsePluginArgCheckBox_CheckedChanged(object sender, EventArgs e)
         {
-            ShowHidePluginArgInput(this.NeedPluginArgCheckBox.Checked);
+            ShowHidePluginArgInput(NeedPluginArgCheckBox.Checked);
         }
     }
 }
diff --git a/shadowsocks-csharp/View/MenuViewController.cs b/shadowsocks-csharp/View/MenuViewController.cs
index 9d44d02b..845f8319 100644
--- a/shadowsocks-csharp/View/MenuViewController.cs
+++ b/shadowsocks-csharp/View/MenuViewController.cs
@@ -438,11 +438,14 @@ namespace Shadowsocks.View
             Configuration configuration = controller.GetConfigurationCopy();
             foreach (var server in configuration.configs)
             {
-                MenuItem item = new MenuItem(server.FriendlyName());
-                item.Tag = i - strategyCount;
-                item.Click += AServerItem_Click;
-                items.Add(i, item);
-                i++;
+                if (Configuration.ChecksServer(server))
+                {
+                    MenuItem item = new MenuItem(server.FriendlyName());
+                    item.Tag = i - strategyCount;
+                    item.Click += AServerItem_Click;
+                    items.Add(i, item);
+                    i++;
+                }
             }
 
             foreach (MenuItem item in items)