diff --git a/src/MaaWpfGui/Helper/ETagCache.cs b/src/MaaWpfGui/Helper/ETagCache.cs
index 8832b9718b..579a795336 100644
--- a/src/MaaWpfGui/Helper/ETagCache.cs
+++ b/src/MaaWpfGui/Helper/ETagCache.cs
@@ -10,6 +10,7 @@
 // This program is distributed in the hope that it will be useful,
 // but WITHOUT ANY WARRANTY
 // </copyright>
+#nullable enable
 
 using System;
 using System.Collections.Generic;
@@ -26,20 +27,20 @@ namespace MaaWpfGui.Helper
         private static readonly ILogger _logger = Log.ForContext<ETagCache>();
 
         private static readonly string _cacheFile = Path.Combine(Environment.CurrentDirectory, "cache/etag.json");
-        private static Dictionary<string, string> _cache;
+        private static Dictionary<string, string> _cache = [];
 
         public static void Load()
         {
             if (File.Exists(_cacheFile) is false)
             {
-                _cache = new Dictionary<string, string>();
+                _cache = [];
                 return;
             }
 
             try
             {
                 var jsonStr = File.ReadAllText(_cacheFile);
-                _cache = JsonConvert.DeserializeObject<Dictionary<string, string>>(jsonStr);
+                _cache = JsonConvert.DeserializeObject<Dictionary<string, string>>(jsonStr) ?? [];
             }
             catch (Exception e)
             {
@@ -47,7 +48,7 @@ namespace MaaWpfGui.Helper
             }
             finally
             {
-                _cache ??= new Dictionary<string, string>();
+                _cache ??= [];
             }
         }
 
@@ -65,7 +66,7 @@ namespace MaaWpfGui.Helper
                 return string.Empty;
             }
 
-            return _cache.TryGetValue(url.Replace("%23", "#"), out string ret) ? ret : string.Empty;
+            return _cache.TryGetValue(url.Replace("%23", "#"), out string? ret) ? ret : string.Empty;
         }
 
         // ReSharper disable once MemberCanBePrivate.Global
@@ -75,18 +76,19 @@ namespace MaaWpfGui.Helper
             Save();
         }
 
-        public static void Set(HttpResponseMessage response)
+        public static void Set(HttpResponseMessage? response)
         {
-            var res = response?.Headers?.ETag?.Tag;
-            if (string.IsNullOrEmpty(res))
+            var etag = response?.Headers?.ETag?.Tag;
+            var uri = response?.RequestMessage?.RequestUri?.ToString();
+            if (string.IsNullOrEmpty(uri) || string.IsNullOrEmpty(etag))
             {
                 return;
             }
 
-            Set(response.RequestMessage.RequestUri.ToString(), res);
+            Set(uri, etag);
         }
 
-        public static async Task<HttpResponseMessage> FetchResponseWithEtag(string url, bool force = false)
+        public static async Task<HttpResponseMessage?> FetchResponseWithEtag(string url, bool force = false)
         {
             var etag = force ? string.Empty : Get(url);
             Dictionary<string, string> headers = new Dictionary<string, string>
diff --git a/src/MaaWpfGui/Helper/HttpResponseHelper.cs b/src/MaaWpfGui/Helper/HttpResponseHelper.cs
index fe61806fd6..3b09237c09 100644
--- a/src/MaaWpfGui/Helper/HttpResponseHelper.cs
+++ b/src/MaaWpfGui/Helper/HttpResponseHelper.cs
@@ -10,6 +10,7 @@
 // This program is distributed in the hope that it will be useful,
 // but WITHOUT ANY WARRANTY
 // </copyright>
+#nullable enable
 
 using System;
 using System.IO;
@@ -23,7 +24,7 @@ namespace MaaWpfGui.Helper
     {
         private static readonly ILogger _logger = Log.ForContext("SourceContext", "HttpResponseHelper");
 
-        public static async Task<bool> SaveResponseToFileAsync(HttpResponseMessage response, string saveTo, bool saveAndDeleteTmp = true)
+        public static async Task<bool> SaveResponseToFileAsync(HttpResponseMessage? response, string saveTo, bool saveAndDeleteTmp = true)
         {
             saveTo = Path.Combine(Environment.CurrentDirectory, saveTo);
 
@@ -37,7 +38,7 @@ namespace MaaWpfGui.Helper
             {
                 using var stream = await GetStreamAsync(response);
                 using var fileStream = new FileStream(tempFile, FileMode.Create, FileAccess.Write, FileShare.None, 8192, true);
-                await stream.CopyToAsync(fileStream).ConfigureAwait(false);
+                await stream!.CopyToAsync(fileStream).ConfigureAwait(false);
             }
             catch (Exception e)
             {
@@ -56,7 +57,7 @@ namespace MaaWpfGui.Helper
         }
 
         // ReSharper disable once MemberCanBePrivate.Global
-        public static async Task<Stream> GetStreamAsync(HttpResponseMessage response)
+        public static async Task<Stream?> GetStreamAsync(HttpResponseMessage? response)
         {
             if (response == null)
             {
@@ -74,7 +75,7 @@ namespace MaaWpfGui.Helper
             }
         }
 
-        public static async Task<string> GetStringAsync(HttpResponseMessage response)
+        public static async Task<string> GetStringAsync(HttpResponseMessage? response)
         {
             if (response == null)
             {
diff --git a/src/MaaWpfGui/Helper/Instances.cs b/src/MaaWpfGui/Helper/Instances.cs
index 2a9fc07885..9818208055 100644
--- a/src/MaaWpfGui/Helper/Instances.cs
+++ b/src/MaaWpfGui/Helper/Instances.cs
@@ -40,7 +40,7 @@ namespace MaaWpfGui.Helper
                 /// <summary>
                 /// Gets 当前理智 / 最大理智
                 /// </summary>
-                public static int[] Sanity { get; } = { -1, -1 };
+                public static int[] Sanity { get; } = [-1, -1];
 
                 public static DateTimeOffset ReportTime { get; set; }
             }
diff --git a/src/MaaWpfGui/Models/ResourceUpdater.cs b/src/MaaWpfGui/Models/ResourceUpdater.cs
index 2d1968d56a..981b5722b8 100644
--- a/src/MaaWpfGui/Models/ResourceUpdater.cs
+++ b/src/MaaWpfGui/Models/ResourceUpdater.cs
@@ -10,6 +10,7 @@
 // This program is distributed in the hope that it will be useful,
 // but WITHOUT ANY WARRANTY
 // </copyright>
+#nullable enable
 
 using System;
 using System.Collections.Generic;
@@ -320,7 +321,7 @@ namespace MaaWpfGui.Models
             return ret;
         }
 
-        private static UpdateResult ResponseToUpdateResult(HttpResponseMessage response)
+        private static UpdateResult ResponseToUpdateResult(HttpResponseMessage? response)
         {
             if (response == null)
             {
@@ -370,7 +371,7 @@ namespace MaaWpfGui.Models
             return updateResult;
         }
 
-        private static ObservableCollection<LogItemViewModel> _logItemViewModels;
+        private static ObservableCollection<LogItemViewModel> _logItemViewModels = [];
 
         private static void OutputDownloadProgress(int index, int count = 0, int maxCount = 1)
         {