diff --git a/clashN/clashN/Base/StringEx.cs b/clashN/clashN/Base/StringEx.cs
index 89621d0..17942a5 100644
--- a/clashN/clashN/Base/StringEx.cs
+++ b/clashN/clashN/Base/StringEx.cs
@@ -4,45 +4,26 @@ namespace ClashN.Base
 {
     static class StringEx
     {
-        public static bool IsNullOrEmpty(this string value)
+        public static bool BeginWithAny(this string? s, IEnumerable<char> chars)
         {
-            return string.IsNullOrEmpty(value);
-        }
+            if (string.IsNullOrEmpty(s))
+                return false;
 
-        public static bool IsNullOrWhiteSpace(this string value)
-        {
-            return string.IsNullOrWhiteSpace(value);
-        }
-
-        public static bool BeginWithAny(this string s, IEnumerable<char> chars)
-        {
-            if (s.IsNullOrEmpty()) return false;
             return chars.Contains(s[0]);
         }
 
-        public static bool IsWhiteSpace(this string value)
-        {
-            foreach (char c in value)
-            {
-                if (char.IsWhiteSpace(c)) continue;
-
-                return false;
-            }
-            return true;
-        }
-
-
         public static IEnumerable<string> NonWhiteSpaceLines(this TextReader reader)
         {
-            string line;
+            string? line;
             while ((line = reader.ReadLine()) != null)
             {
-                if (line.IsWhiteSpace()) continue;
+                if (string.IsNullOrWhiteSpace(line))
+                    continue;
                 yield return line;
             }
         }
 
-        public static string TrimEx(this string value)
+        public static string TrimEx(this string? value)
         {
             return value == null ? string.Empty : value.Trim();
         }
diff --git a/clashN/clashN/Handler/ConfigProc.cs b/clashN/clashN/Handler/ConfigProc.cs
index 34adf92..396fd13 100644
--- a/clashN/clashN/Handler/ConfigProc.cs
+++ b/clashN/clashN/Handler/ConfigProc.cs
@@ -1,5 +1,6 @@
 using ClashN.Mode;
 using ClashN.Tool;
+using System.Collections.Specialized;
 using System.IO;
 using System.Web;
 
@@ -93,9 +94,7 @@ namespace ClashN.Handler
                 config.ConstItem.defIEProxyExceptions = Global.IEProxyExceptions;
             }
 
-            if (config == null
-                || config.ProfileItems.Count <= 0
-                )
+            if (config.ProfileItems.Count <= 0)
             {
                 Global.reloadCore = false;
             }
@@ -114,7 +113,7 @@ namespace ClashN.Handler
                 }
             }
 
-            LazyConfig.Instance.SetConfig(ref config);
+            LazyConfig.Instance.SetConfig(config);
             return 0;
         }
         /// <summary>
@@ -262,7 +261,7 @@ namespace ClashN.Handler
             }
             return -1;
         }
-        public static ProfileItem GetDefaultProfile(ref Config config)
+        public static ProfileItem? GetDefaultProfile(ref Config config)
         {
             if (config.ProfileItems.Count <= 0)
             {
@@ -571,13 +570,15 @@ namespace ClashN.Handler
                 Uri url = new Uri(clipboardData);
                 if (url.Host == "install-config")
                 {
-                    var query = HttpUtility.ParseQueryString(url.Query);
+                    NameValueCollection query =
+                        HttpUtility.ParseQueryString(url.Query);
+
                     if (!string.IsNullOrEmpty(query["url"] ?? ""))
                     {
                         ProfileItem item = new ProfileItem()
                         {
                             groupId = groupId,
-                            url = query["url"],
+                            url = query["url"] ?? string.Empty,
                             coreType = CoreKind.ClashMeta,
                             address = string.Empty,
                             enabled = true,
@@ -613,15 +614,12 @@ namespace ClashN.Handler
             else
             { return -1; }
 
-            ProfileItem profileItem;
+            ProfileItem? profileItem = null;
             if (!string.IsNullOrEmpty(indexId))
-            {
                 profileItem = config.GetProfileItem(indexId);
-            }
-            else
-            {
+
+            if (profileItem == null)
                 profileItem = new ProfileItem();
-            }
             profileItem.groupId = groupId;
 
             if (AddProfileViaContent(ref config, profileItem, clipboardData) == 0)
diff --git a/clashN/clashN/Handler/DownloadHandle.cs b/clashN/clashN/Handler/DownloadHandle.cs
index aaa2e58..d150a59 100644
--- a/clashN/clashN/Handler/DownloadHandle.cs
+++ b/clashN/clashN/Handler/DownloadHandle.cs
@@ -70,7 +70,7 @@ namespace ClashN.Handler
         /// DownloadString
         /// </summary> 
         /// <param name="url"></param>
-        public async Task<(string, HttpResponseHeaders)> DownloadStringAsync(string url, bool blProxy, string userAgent)
+        public async Task<(string, HttpResponseHeaders)?> DownloadStringAsync(string url, bool blProxy, string userAgent)
         {
             try
             {
@@ -108,10 +108,11 @@ namespace ClashN.Handler
                     Error?.Invoke(this, new ErrorEventArgs(ex.InnerException));
                 }
             }
-            return (null, null);
+
+            return null;
         }
 
-        public async Task<string> UrlRedirectAsync(string url, bool blProxy)
+        public async Task<string?> UrlRedirectAsync(string url, bool blProxy)
         {
             Utils.SetSecurityProtocol(LazyConfig.Instance.Config.EnableSecurityProtocolTls13);
             SocketsHttpHandler webRequestHandler = new SocketsHttpHandler
@@ -124,7 +125,7 @@ namespace ClashN.Handler
             HttpResponseMessage response = await client.GetAsync(url);
             if (response.StatusCode.ToString() == "Redirect")
             {
-                return response.Headers.Location.ToString();
+                return response.Headers.Location?.ToString();
             }
             else
             {
diff --git a/clashN/clashN/Handler/LazyConfig.cs b/clashN/clashN/Handler/LazyConfig.cs
index b645aba..7ee855e 100644
--- a/clashN/clashN/Handler/LazyConfig.cs
+++ b/clashN/clashN/Handler/LazyConfig.cs
@@ -15,7 +15,7 @@ namespace ClashN.Handler
         {
             get { return _instance.Value; }
         }
-        public void SetConfig(ref Config config)
+        public void SetConfig(Config config)
         {
             _config = config;
         }
diff --git a/clashN/clashN/Handler/UpdateHandle.cs b/clashN/clashN/Handler/UpdateHandle.cs
index 09770c2..f2faab5 100644
--- a/clashN/clashN/Handler/UpdateHandle.cs
+++ b/clashN/clashN/Handler/UpdateHandle.cs
@@ -218,10 +218,10 @@ namespace ClashN.Handler
                     {
                         _updateFunc(false, $"{hashCode}{args.GetException().Message}");
                     };
-                    var result = await downloadHandle.DownloadStringAsync(url, blProxy, userAgent);
+                    var result = (await downloadHandle.DownloadStringAsync(url, blProxy, userAgent)) ?? throw new Exception();
                     if (blProxy && string.IsNullOrEmpty(result.Item1))
                     {
-                        result = await downloadHandle.DownloadStringAsync(url, false, userAgent);
+                        result = (await downloadHandle.DownloadStringAsync(url, false, userAgent)) ?? throw new Exception();
                     }
 
                     if (string.IsNullOrEmpty(result.Item1))
diff --git a/clashN/clashN/Mode/Config.cs b/clashN/clashN/Mode/Config.cs
index 83ea6f2..1a73a28 100644
--- a/clashN/clashN/Mode/Config.cs
+++ b/clashN/clashN/Mode/Config.cs
@@ -74,12 +74,11 @@ namespace ClashN.Mode
             return ProfileItems.FindIndex(it => it.indexId == id);
         }
 
-        public ProfileItem GetProfileItem(string id)
+        public ProfileItem? GetProfileItem(string id)
         {
             if (string.IsNullOrEmpty(id))
-            {
                 return null;
-            }
+
             return ProfileItems.FirstOrDefault(it => it.indexId == id);
         }
 
@@ -160,7 +159,7 @@ namespace ClashN.Mode
 
         public bool colorModeDark { get; set; }
         public string? colorPrimaryName { get; set; }
-        public string currentFontFamily { get; set; }
+        public string currentFontFamily { get; set; } = string.Empty;
         public int currentFontSize { get; set; }
 
         public int proxiesSorting { get; set; }
@@ -174,21 +173,9 @@ namespace ClashN.Mode
     [Serializable]
     public class ConstItem
     {
-        public string subConvertUrl
-        {
-            get; set;
-        }
-        public string speedTestUrl
-        {
-            get; set;
-        }
-        public string speedPingTestUrl
-        {
-            get; set;
-        }
-        public string defIEProxyExceptions
-        {
-            get; set;
-        }
+        public string subConvertUrl { get; set; } = string.Empty;
+        public string speedTestUrl { get; set; } = string.Empty;
+        public string speedPingTestUrl { get; set; } = string.Empty;
+        public string defIEProxyExceptions { get; set; } = string.Empty;
     }
 }
diff --git a/clashN/clashN/ViewModels/ConnectionsViewModel.cs b/clashN/clashN/ViewModels/ConnectionsViewModel.cs
index daaa72e..0388cbf 100644
--- a/clashN/clashN/ViewModels/ConnectionsViewModel.cs
+++ b/clashN/clashN/ViewModels/ConnectionsViewModel.cs
@@ -50,7 +50,7 @@ namespace ClashN.ViewModels
 
             var canEditRemove = this.WhenAnyValue(
              x => x.SelectedSource,
-             selectedSource => selectedSource != null && !selectedSource.id.IsNullOrEmpty());
+             selectedSource => selectedSource != null && !string.IsNullOrEmpty(selectedSource.id));
 
             this.WhenAnyValue(
               x => x.SortingSelected,
@@ -144,7 +144,7 @@ namespace ClashN.ViewModels
                 model.id = item.Id;
                 model.network = item.metadata.Network;
                 model.type = item.metadata.Type;
-                model.host = $"{(item.metadata.Host.IsNullOrEmpty() ? item.metadata.DestinationIP : item.metadata.Host)}:{item.metadata.DestinationPort}";
+                model.host = $"{(string.IsNullOrEmpty(item.metadata.Host) ? item.metadata.DestinationIP : item.metadata.Host)}:{item.metadata.DestinationPort}";
                 var sp = (dtNow - item.start);
                 model.time = sp.TotalSeconds < 0 ? 1 : sp.TotalSeconds;
                 model.upload = item.upload;
diff --git a/clashN/clashN/ViewModels/MainWindowViewModel.cs b/clashN/clashN/ViewModels/MainWindowViewModel.cs
index 267992d..a2af488 100644
--- a/clashN/clashN/ViewModels/MainWindowViewModel.cs
+++ b/clashN/clashN/ViewModels/MainWindowViewModel.cs
@@ -460,7 +460,7 @@ namespace ClashN.ViewModels
         {
             ModifyTheme(_config.UiItem.colorModeDark);
 
-            if (!_config.UiItem.colorPrimaryName.IsNullOrEmpty())
+            if (!string.IsNullOrEmpty(_config.UiItem.colorPrimaryName))
             {
                 var swatch = new SwatchesProvider().Swatches.FirstOrDefault(t => t.Name == _config.UiItem.colorPrimaryName);
                 if (swatch != null
diff --git a/clashN/clashN/ViewModels/ProfileEditViewModel.cs b/clashN/clashN/ViewModels/ProfileEditViewModel.cs
index 8008183..51b85cc 100644
--- a/clashN/clashN/ViewModels/ProfileEditViewModel.cs
+++ b/clashN/clashN/ViewModels/ProfileEditViewModel.cs
@@ -34,7 +34,7 @@ namespace ClashN.ViewModels
             _noticeHandler = Locator.Current.GetService<NoticeHandler>();
             _config = LazyConfig.Instance.Config;
 
-            if (profileItem.indexId.IsNullOrEmpty())
+            if (string.IsNullOrEmpty(profileItem.indexId))
             {
                 SelectedSource = profileItem;
             }
diff --git a/clashN/clashN/ViewModels/ProfilesViewModel.cs b/clashN/clashN/ViewModels/ProfilesViewModel.cs
index 8b8a42d..40e81b1 100644
--- a/clashN/clashN/ViewModels/ProfilesViewModel.cs
+++ b/clashN/clashN/ViewModels/ProfilesViewModel.cs
@@ -59,7 +59,7 @@ namespace ClashN.ViewModels
 
             var canEditRemove = this.WhenAnyValue(
                x => x.SelectedSource,
-               selectedSource => selectedSource != null && !selectedSource.indexId.IsNullOrEmpty());
+               selectedSource => selectedSource != null && !string.IsNullOrEmpty(selectedSource.indexId));
 
             //Profile
             EditLocalFileCmd = ReactiveCommand.Create(() =>
diff --git a/clashN/clashN/ViewModels/ProxiesViewModel.cs b/clashN/clashN/ViewModels/ProxiesViewModel.cs
index d5c42d3..5d8a59d 100644
--- a/clashN/clashN/ViewModels/ProxiesViewModel.cs
+++ b/clashN/clashN/ViewModels/ProxiesViewModel.cs
@@ -65,7 +65,7 @@ namespace ClashN.ViewModels
             //GetClashProxies(true);
             this.WhenAnyValue(
                x => x.SelectedGroup,
-               y => y != null && !y.name.IsNullOrEmpty())
+               y => y != null && !string.IsNullOrEmpty(y.name))
                    .Subscribe(c => RefreshProxyDetails(c));
 
             this.WhenAnyValue(
@@ -268,7 +268,7 @@ namespace ClashN.ViewModels
                     continue;
                 }
                 var item = _proxyGroups.Where(t => t.name == kv.Key).FirstOrDefault();
-                if (item != null && !item.name.IsNullOrEmpty())
+                if (item != null && !string.IsNullOrEmpty(item.name))
                 {
                     continue;
                 }
@@ -379,11 +379,11 @@ namespace ClashN.ViewModels
 
         public void SetActiveProxy()
         {
-            if (SelectedGroup == null || SelectedGroup.name.IsNullOrEmpty())
+            if (SelectedGroup == null || string.IsNullOrEmpty(SelectedGroup.name))
             {
                 return;
             }
-            if (SelectedDetail == null || SelectedDetail.name.IsNullOrEmpty())
+            if (SelectedDetail == null || string.IsNullOrEmpty(SelectedDetail.name))
             {
                 return;
             }
diff --git a/clashN/clashN/ViewModels/SettingsViewModel.cs b/clashN/clashN/ViewModels/SettingsViewModel.cs
index 3a29e1d..b3fafb8 100644
--- a/clashN/clashN/ViewModels/SettingsViewModel.cs
+++ b/clashN/clashN/ViewModels/SettingsViewModel.cs
@@ -141,7 +141,7 @@ namespace ClashN.ViewModels
             //UI
             ColorModeDark = _config.UiItem.colorModeDark;
             _swatches.AddRange(new SwatchesProvider().Swatches);
-            if (!_config.UiItem.colorPrimaryName.IsNullOrEmpty())
+            if (!string.IsNullOrEmpty(_config.UiItem.colorPrimaryName))
             {
                 SelectedSwatch = _swatches.FirstOrDefault(t => t.Name == _config.UiItem.colorPrimaryName);
             }
@@ -163,11 +163,11 @@ namespace ClashN.ViewModels
 
             this.WhenAnyValue(
               x => x.SelectedSwatch,
-              y => y != null && !y.Name.IsNullOrEmpty())
+              y => y != null && !string.IsNullOrEmpty(y.Name))
                  .Subscribe(c =>
                  {
                      if (SelectedSwatch == null
-                     || SelectedSwatch.Name.IsNullOrEmpty()
+                     || string.IsNullOrEmpty(SelectedSwatch.Name)
                      || SelectedSwatch.ExemplarHue == null
                      || SelectedSwatch.ExemplarHue?.Color == null)
                      {
@@ -183,7 +183,7 @@ namespace ClashN.ViewModels
 
             this.WhenAnyValue(
              x => x.CurrentLanguage,
-             y => y != null && !y.IsNullOrEmpty())
+             y => y != null && !string.IsNullOrEmpty(y))
                 .Subscribe(c =>
                 {
                     if (!string.IsNullOrEmpty(CurrentLanguage))
diff --git a/clashN/clashN/Views/ProxiesView.xaml b/clashN/clashN/Views/ProxiesView.xaml
index c485a15..15b4922 100644
--- a/clashN/clashN/Views/ProxiesView.xaml
+++ b/clashN/clashN/Views/ProxiesView.xaml
@@ -163,7 +163,7 @@
                 </ListView.ItemsPanel>
                 <ListView.ItemTemplate>
                     <DataTemplate>
-                        <Border Width="160" Padding="0">
+                        <Border Width="160" Padding="0" KeyDown="ProxyItem_KeyDown">
                             <DockPanel>
                                 <Border
                                     Width="5"
diff --git a/clashN/clashN/Views/ProxiesView.xaml.cs b/clashN/clashN/Views/ProxiesView.xaml.cs
index ecf0f95..414f30f 100644
--- a/clashN/clashN/Views/ProxiesView.xaml.cs
+++ b/clashN/clashN/Views/ProxiesView.xaml.cs
@@ -43,15 +43,29 @@ namespace ClashN.Views
 
         private void ProxiesView_KeyDown(object sender, KeyEventArgs e)
         {
-            if (Keyboard.IsKeyDown(Key.F5))
+            switch (e.Key)
             {
-                ViewModel?.ProxiesReload();
+                case Key.F5:
+                    ViewModel?.ProxiesReload();
+                    break;
+                case Key.Enter:
+                    ViewModel?.SetActiveProxy();
+                    break;
             }
-            else if (Keyboard.IsKeyDown(Key.Enter))
+        }
+
+
+        private object? lastProxyItemKeyDownSender;
+        private int lastProxyItemKeyDownTimestamp;
+        private void ProxyItem_KeyDown(object sender, KeyEventArgs e)
+        {
+            if (sender == lastProxyItemKeyDownSender && e.Timestamp - lastProxyItemKeyDownTimestamp < 500)
             {
                 ViewModel?.SetActiveProxy();
             }
 
+            lastProxyItemKeyDownSender = sender;
+            lastProxyItemKeyDownTimestamp = e.Timestamp;
         }
     }
 }