diff --git a/c#/GlobalSuppressions.cs b/c#/GlobalSuppressions.cs
index bfd97d2f..cb28700d 100644
--- a/c#/GlobalSuppressions.cs
+++ b/c#/GlobalSuppressions.cs
@@ -83,6 +83,7 @@
 [assembly: SuppressMessage("StyleCop.CSharp.ReadabilityRules", "SA1122:Use string.Empty for empty strings")]
 [assembly: SuppressMessage("StyleCop.CSharp.ReadabilityRules", "SA1127:Generic type constraints should be on their own line")]
 [assembly: SuppressMessage("StyleCop.CSharp.ReadabilityRules", "SA1128:Put constructor initializers on their own line")]
+[assembly: SuppressMessage("StyleCop.CSharp.ReadabilityRules", "SA1133:Each attribute should be placed on its own line of code")]
 [assembly: SuppressMessage("StyleCop.CSharp.ReadabilityRules", "SA1134:Attributes should not share line")]
 [assembly: SuppressMessage("StyleCop.CSharp.SpacingRules", "SA1008:Opening parenthesis should be spaced correctly")]
 [assembly: SuppressMessage("StyleCop.CSharp.SpacingRules", "SA1009:Closing parenthesis should be spaced correctly")]
diff --git a/c#/crawler/src/SonicPusher.cs b/c#/crawler/src/SonicPusher.cs
index 6b3101a3..276aa5fb 100644
--- a/c#/crawler/src/SonicPusher.cs
+++ b/c#/crawler/src/SonicPusher.cs
@@ -14,7 +14,7 @@ public SonicPusher(ILogger<SonicPusher> logger, IConfiguration config)
             _config.GetValue("Hostname", "localhost"),
             _config.GetValue("Port", 1491),
             _config.GetValue("Secret", "SecretPassword"));
-        CollectionPrefix = _config.GetValue<string>("CollectionPrefix") ?? "tbm_";
+        CollectionPrefix = _config.GetValue<string>("CollectionPrefix", "tbm_");
     }
 
     public ISonicIngestConnection Ingest { get; }
diff --git a/c#/crawler/src/Tieba/ClientRequester.cs b/c#/crawler/src/Tieba/ClientRequester.cs
index 2d1fa3ee..fda5cd2a 100644
--- a/c#/crawler/src/Tieba/ClientRequester.cs
+++ b/c#/crawler/src/Tieba/ClientRequester.cs
@@ -100,7 +100,7 @@ private async Task<HttpResponseMessage> PostJson(
             return acc;
         }) + "tiebaclient!!!";
 #pragma warning disable CA5351 // Do Not Use Broken Cryptographic Algorithms
-        var signatureMd5 = BitConverter.ToString(MD5.HashData(Encoding.UTF8.GetBytes(signature))).Replace("-", "");
+        var signatureMd5 = Convert.ToHexString(MD5.HashData(Encoding.UTF8.GetBytes(signature)));
 #pragma warning restore CA5351 // Do Not Use Broken Cryptographic Algorithms
         postParamPairs.Add(KeyValuePair.Create("sign", signatureMd5));
 
diff --git a/c#/crawler/src/Tieba/ClientRequesterTcs.cs b/c#/crawler/src/Tieba/ClientRequesterTcs.cs
index 7c5fcbcc..77e6a15d 100644
--- a/c#/crawler/src/Tieba/ClientRequesterTcs.cs
+++ b/c#/crawler/src/Tieba/ClientRequesterTcs.cs
@@ -7,7 +7,6 @@ public sealed class ClientRequesterTcs : WithLogTrace
     private readonly ConcurrentQueue<TaskCompletionSource> _queue = new();
     private readonly Timer _timer = new() {Enabled = true};
     private readonly Stopwatch _stopwatch = new();
-    private double _maxRps;
     private uint _requestCounter;
 
     public ClientRequesterTcs(ILogger<ClientRequesterTcs> logger, IConfiguration config)
@@ -28,10 +27,10 @@ public ClientRequesterTcs(ILogger<ClientRequesterTcs> logger, IConfiguration con
     private float AverageRps => _requestCounter / (float)_stopwatch.Elapsed.TotalSeconds;
     private double MaxRps
     {
-        get => _maxRps;
+        get;
         set
         {
-            _maxRps = value;
+            field = value;
             if ((uint)_timer.Interval != (uint)(1000 / value))
             { // only update interval with a truncated integer to prevent frequently change it
                 // which will cause the increment of real rps can't keep up with _maxRps with long queue length
diff --git a/c#/crawler/src/Tieba/Crawl/Crawler/CrawlerLocks.cs b/c#/crawler/src/Tieba/Crawl/Crawler/CrawlerLocks.cs
index 729d86b2..2deb7362 100644
--- a/c#/crawler/src/Tieba/Crawl/Crawler/CrawlerLocks.cs
+++ b/c#/crawler/src/Tieba/Crawl/Crawler/CrawlerLocks.cs
@@ -95,10 +95,11 @@ public IReadOnlyDictionary<LockId, IReadOnlyDictionary<Page, FailureCount>> Retr
     {
         lock (_failed)
         {
-            var failedClone = _failed.ToDictionary(pair => pair.Key, pair =>
+            var failedClone = _failed.ToDictionary(pair => pair.Key,
+                IReadOnlyDictionary<Page, FailureCount> (pair) =>
             {
                 lock (pair.Value)
-                    return (IReadOnlyDictionary<Page, FailureCount>)new Dictionary<Page, FailureCount>(pair.Value);
+                    return new Dictionary<Page, FailureCount>(pair.Value);
             });
             _failed.Clear();
             return failedClone;
diff --git a/c#/crawler/src/Tieba/Crawl/Facade/CrawlFacade.cs b/c#/crawler/src/Tieba/Crawl/Facade/CrawlFacade.cs
index e3f7e275..e6653430 100644
--- a/c#/crawler/src/Tieba/Crawl/Facade/CrawlFacade.cs
+++ b/c#/crawler/src/Tieba/Crawl/Facade/CrawlFacade.cs
@@ -19,7 +19,6 @@ public abstract class CrawlFacade<TPostEntity, TParsedPost, TResponse, TPostProt
 {
     private readonly HashSet<Page> _lockingPages = [];
     private readonly ConcurrentDictionary<Uid, User.Parsed> _users = new();
-    private UserParser? _userParser;
     private ICrawlFacade<TPostEntity, TParsedPost>.ExceptionHandler _exceptionHandler = _ => { };
 
     // ReSharper disable UnusedAutoPropertyAccessor.Global
@@ -31,7 +30,9 @@ public required ILogger<CrawlFacade<TPostEntity, TParsedPost, TResponse, TPostPr
     // ReSharper restore UnusedAutoPropertyAccessor.Global
     protected Fid Fid { get; } = fid;
     protected ConcurrentDictionary<PostId, TParsedPost> Posts { get; } = new();
-    protected UserParser UserParser => _userParser ??= userParserFactory(_users);
+
+    [field: AllowNull, MaybeNull]
+    protected UserParser UserParser => field ??= userParserFactory(_users);
 
     public virtual void Dispose()
     {
diff --git a/c#/crawler/src/Tieba/Crawl/Saver/IRevisionProperties.cs b/c#/crawler/src/Tieba/Crawl/Saver/IRevisionProperties.cs
index 7086bf96..47ebb83b 100644
--- a/c#/crawler/src/Tieba/Crawl/Saver/IRevisionProperties.cs
+++ b/c#/crawler/src/Tieba/Crawl/Saver/IRevisionProperties.cs
@@ -6,6 +6,7 @@ public interface IRevisionProperties
         [typeof(ThreadRevision), typeof(ReplyRevision), typeof(SubReplyRevision), typeof(UserRevision)]);
 
     private static IReadOnlyDictionary<Type, IReadOnlyDictionary<string, PropertyInfo>> GetPropsKeyByType(IEnumerable<Type> types) =>
-        types.ToDictionary(type => type, type =>
-            (IReadOnlyDictionary<string, PropertyInfo>)type.GetProperties().ToDictionary(prop => prop.Name));
+        types.ToDictionary(type => type,
+            IReadOnlyDictionary<string, PropertyInfo> (type) =>
+            type.GetProperties().ToDictionary(prop => prop.Name));
 }
diff --git a/c#/crawler/src/Tieba/Crawl/Saver/Post/ReplySaver.cs b/c#/crawler/src/Tieba/Crawl/Saver/Post/ReplySaver.cs
index 2504ba5d..fe354045 100644
--- a/c#/crawler/src/Tieba/Crawl/Saver/Post/ReplySaver.cs
+++ b/c#/crawler/src/Tieba/Crawl/Saver/Post/ReplySaver.cs
@@ -26,10 +26,10 @@ public partial class ReplySaver(
 }
 public partial class ReplySaver
 {
-    private Lazy<Dictionary<Type, AddSplitRevisionsDelegate>>? _addSplitRevisionsDelegatesKeyByEntityType;
+    [field: AllowNull, MaybeNull]
     protected override Lazy<Dictionary<Type, AddSplitRevisionsDelegate>>
         AddSplitRevisionsDelegatesKeyByEntityType =>
-        _addSplitRevisionsDelegatesKeyByEntityType ??= new(() => new()
+        field ??= new(() => new()
         {
             {typeof(ReplyRevision.SplitFloor), AddRevisionsWithDuplicateIndex<ReplyRevision.SplitFloor>},
             {typeof(ReplyRevision.SplitSubReplyCount), AddRevisionsWithDuplicateIndex<ReplyRevision.SplitSubReplyCount>},
diff --git a/c#/crawler/src/Tieba/Crawl/Saver/Post/SubReplySaver.cs b/c#/crawler/src/Tieba/Crawl/Saver/Post/SubReplySaver.cs
index dd7b0c4d..ee497a0a 100644
--- a/c#/crawler/src/Tieba/Crawl/Saver/Post/SubReplySaver.cs
+++ b/c#/crawler/src/Tieba/Crawl/Saver/Post/SubReplySaver.cs
@@ -22,10 +22,10 @@ public partial class SubReplySaver(
 }
 public partial class SubReplySaver
 {
-    private Lazy<Dictionary<Type, AddSplitRevisionsDelegate>>? _addSplitRevisionsDelegatesKeyByEntityType;
+    [field: AllowNull, MaybeNull]
     protected override Lazy<Dictionary<Type, AddSplitRevisionsDelegate>>
         AddSplitRevisionsDelegatesKeyByEntityType =>
-        _addSplitRevisionsDelegatesKeyByEntityType ??= new(() => new()
+        field ??= new(() => new()
         {
             {typeof(SubReplyRevision.SplitAgreeCount), AddRevisionsWithDuplicateIndex<SubReplyRevision.SplitAgreeCount>},
             {typeof(SubReplyRevision.SplitDisagreeCount), AddRevisionsWithDuplicateIndex<SubReplyRevision.SplitDisagreeCount>}
diff --git a/c#/crawler/src/Tieba/Crawl/Saver/Post/ThreadSaver.cs b/c#/crawler/src/Tieba/Crawl/Saver/Post/ThreadSaver.cs
index 84381b14..5e2119a5 100644
--- a/c#/crawler/src/Tieba/Crawl/Saver/Post/ThreadSaver.cs
+++ b/c#/crawler/src/Tieba/Crawl/Saver/Post/ThreadSaver.cs
@@ -21,10 +21,10 @@ public partial class ThreadSaver(
 }
 public partial class ThreadSaver
 {
-    private Lazy<Dictionary<Type, AddSplitRevisionsDelegate>>? _addSplitRevisionsDelegatesKeyByEntityType;
+    [field: AllowNull, MaybeNull]
     protected override Lazy<Dictionary<Type, AddSplitRevisionsDelegate>>
         AddSplitRevisionsDelegatesKeyByEntityType =>
-        _addSplitRevisionsDelegatesKeyByEntityType ??= new(() => new()
+        field ??= new(() => new()
         {
             {typeof(ThreadRevision.SplitViewCount), AddRevisionsWithDuplicateIndex<ThreadRevision.SplitViewCount>}
         });
diff --git a/c#/crawler/src/Tieba/Crawl/Saver/Related/AuthorRevisionSaver.cs b/c#/crawler/src/Tieba/Crawl/Saver/Related/AuthorRevisionSaver.cs
index 41ef2bc1..81124a18 100644
--- a/c#/crawler/src/Tieba/Crawl/Saver/Related/AuthorRevisionSaver.cs
+++ b/c#/crawler/src/Tieba/Crawl/Saver/Related/AuthorRevisionSaver.cs
@@ -91,7 +91,7 @@ private Action Save<TEntity, TRevision, TValue>(
     // locking key only using AuthorRevision.Fid and Uid, ignoring TriggeredBy
     // this prevents inserting multiple entities with similar time and other fields with the same values
     // ReSharper disable NotAccessedPositionalProperty.Global
-    public record UniqueAuthorRevision(Fid Fid, Uid Uid);
+    private sealed record UniqueAuthorRevision(Fid Fid, Uid Uid);
 
     // ReSharper restore NotAccessedPositionalProperty.Global
     private sealed class LatestAuthorRevisionProjection<TValue>
diff --git a/c#/crawler/src/Tieba/Crawl/Saver/UserSaver.cs b/c#/crawler/src/Tieba/Crawl/Saver/UserSaver.cs
index ff72db68..7b812415 100644
--- a/c#/crawler/src/Tieba/Crawl/Saver/UserSaver.cs
+++ b/c#/crawler/src/Tieba/Crawl/Saver/UserSaver.cs
@@ -61,10 +61,10 @@ public void SaveParentThreadLatestReplierUid(CrawlerDbContext db, Tid tid) =>
 }
 public partial class UserSaver
 {
-    private Lazy<Dictionary<Type, AddSplitRevisionsDelegate>>? _addSplitRevisionsDelegatesKeyByEntityType;
+    [field: AllowNull, MaybeNull]
     protected override Lazy<Dictionary<Type, AddSplitRevisionsDelegate>>
         AddSplitRevisionsDelegatesKeyByEntityType =>
-        _addSplitRevisionsDelegatesKeyByEntityType ??= new(() => new()
+        field ??= new(() => new()
         {
             {typeof(UserRevision.SplitDisplayName), AddRevisionsWithDuplicateIndex<UserRevision.SplitDisplayName>},
             {typeof(UserRevision.SplitPortraitUpdatedAt), AddRevisionsWithDuplicateIndex<UserRevision.SplitPortraitUpdatedAt>},
diff --git a/c#/imagePipeline/src/Consumer/MetadataConsumer.cs b/c#/imagePipeline/src/Consumer/MetadataConsumer.cs
index b37272c8..3d12c0c8 100644
--- a/c#/imagePipeline/src/Consumer/MetadataConsumer.cs
+++ b/c#/imagePipeline/src/Consumer/MetadataConsumer.cs
@@ -242,7 +242,7 @@ private static class ExifGpsTagValuesParser
                 : null;
         }
 
-        private static double ConvertDmsToDd(IReadOnlyList<double> dms)
+        private static double ConvertDmsToDd(List<double> dms)
         { // https://stackoverflow.com/questions/3249700/convert-degrees-minutes-seconds-to-decimal-coordinates
             if (dms.Count != 3) throw new ArgumentException(
                 "Unexpected length for DMS, expecting three doubles.", nameof(dms));
diff --git a/c#/imagePipeline/src/Consumer/QrCodeConsumer.cs b/c#/imagePipeline/src/Consumer/QrCodeConsumer.cs
index 4f04de60..19c89a17 100644
--- a/c#/imagePipeline/src/Consumer/QrCodeConsumer.cs
+++ b/c#/imagePipeline/src/Consumer/QrCodeConsumer.cs
@@ -9,7 +9,7 @@ public QrCodeConsumer(IConfiguration config, FailedImageHandler failedImageHandl
     {
         _failedImageHandler = failedImageHandler;
         var modelsPath = config.GetSection("QrCodeConsumer")
-            .GetValue("ModelPath", "./OpenCvWechatModels") ?? "./OpenCvWechatModels";
+            .GetValue("ModelPath", "./OpenCvWechatModels");
         _qrCode = WeChatQRCode.Create(
             $"{modelsPath}/detect.prototxt",
             $"{modelsPath}/detect.caffemodel",
diff --git a/c#/imagePipeline/src/ImageBatchConsumingWorker.cs b/c#/imagePipeline/src/ImageBatchConsumingWorker.cs
index 574d9144..1f5c6ada 100644
--- a/c#/imagePipeline/src/ImageBatchConsumingWorker.cs
+++ b/c#/imagePipeline/src/ImageBatchConsumingWorker.cs
@@ -43,7 +43,7 @@ protected override async Task DoWork(CancellationToken stoppingToken)
     }
 
     private async Task Consume(
-        IReadOnlyCollection<ImageWithBytes> imagesWithBytes,
+        List<ImageWithBytes> imagesWithBytes,
         CancellationToken stoppingToken = default)
     {
         await using var dbFactory = dbContextDefaultFactory();
diff --git a/c#/imagePipeline/src/Ocr/PaddleOcrProvider.cs b/c#/imagePipeline/src/Ocr/PaddleOcrProvider.cs
index e340ea74..38c4f999 100644
--- a/c#/imagePipeline/src/Ocr/PaddleOcrProvider.cs
+++ b/c#/imagePipeline/src/Ocr/PaddleOcrProvider.cs
@@ -18,8 +18,7 @@ public PaddleOcrProvider(IConfiguration config, string script,
     {
         _config = config.GetSection("OcrConsumer:PaddleOcr");
         _script = script;
-        Settings.GlobalModelDirectory =
-            _config.GetValue("ModelPath", "./PaddleOcrModels") ?? "./PaddleOcrModels";
+        Settings.GlobalModelDirectory = _config.GetValue("ModelPath", "./PaddleOcrModels");
         _paddleOcrDetectorFactory = paddleOcrDetectorFactory;
         _paddleOcrRecognizerFactory = paddleOcrRecognizerFactory;
     }
diff --git a/c#/imagePipeline/src/Ocr/TesseractRecognizer.cs b/c#/imagePipeline/src/Ocr/TesseractRecognizer.cs
index e2813749..d9509afb 100644
--- a/c#/imagePipeline/src/Ocr/TesseractRecognizer.cs
+++ b/c#/imagePipeline/src/Ocr/TesseractRecognizer.cs
@@ -5,13 +5,12 @@ namespace tbm.ImagePipeline.Ocr;
 public sealed partial class TesseractRecognizer(IConfiguration config, string script) : IDisposable
 {
     private readonly IConfigurationSection _config = config.GetSection("OcrConsumer:Tesseract");
-    private Lazy<OCRTesseract>? _tesseractInstanceHorizontal;
-    private Lazy<OCRTesseract>? _tesseractInstanceVertical;
 
     public delegate TesseractRecognizer New(string script);
 
     [SuppressMessage("ReSharper", "StringLiteralTypo")]
-    private Lazy<OCRTesseract> TesseractInstanceHorizontal => _tesseractInstanceHorizontal ??= new(script switch
+    [field: AllowNull, MaybeNull]
+    private Lazy<OCRTesseract> TesseractInstanceHorizontal => field ??= new(script switch
     { // https://en.wikipedia.org/wiki/Template:ISO_15924_script_codes_and_related_Unicode_data
         "Hans" => CreateTesseract("best/chi_sim+best/eng"),
         "Hant" => CreateTesseract("best/chi_tra+best/eng"),
@@ -21,7 +20,8 @@ public sealed partial class TesseractRecognizer(IConfiguration config, string sc
     });
 
     [SuppressMessage("ReSharper", "StringLiteralTypo")]
-    private Lazy<OCRTesseract> TesseractInstanceVertical => _tesseractInstanceVertical ??= new(script switch
+    [field: AllowNull, MaybeNull]
+    private Lazy<OCRTesseract> TesseractInstanceVertical => field ??= new(script switch
     {
         "Hans" => CreateTesseract("best/chi_sim_vert", isVertical: true),
         "Hant" => CreateTesseract("best/chi_tra_vert", isVertical: true),
@@ -43,7 +43,7 @@ public void Dispose()
     // https://github.com/shimat/opencvsharp/issues/873#issuecomment-1458868153
     // https://pyimagesearch.com/2021/11/15/tesseract-page-segmentation-modes-psms-explained-how-to-improve-your-ocr-accuracy/
     private OCRTesseract CreateTesseract(string scripts, bool isVertical = false) =>
-        OCRTesseract.Create(_config.GetValue("DataPath", "") ?? "",
+        OCRTesseract.Create(_config.GetValue("DataPath", ""),
             scripts, charWhitelist: "", oem: 1, psmode: isVertical ? 5 : 7);
 }
 public sealed partial class TesseractRecognizer