diff --git a/c#/crawler/src/Worker/ForumModeratorRevisionCrawlWorker.cs b/c#/crawler/src/Worker/ForumModeratorRevisionCrawlWorker.cs
index a478de1c..2929df76 100644
--- a/c#/crawler/src/Worker/ForumModeratorRevisionCrawlWorker.cs
+++ b/c#/crawler/src/Worker/ForumModeratorRevisionCrawlWorker.cs
@@ -50,7 +50,7 @@ where e.IsCrawling
                     ?.GetAttribute("href")?.Split("/home/main?id=")[1].NullIfEmpty())
                 .OfType<string>();
             return memberPortraits.Select(portrait => (type, portrait));
-        }).SelectMany(i => i);
+        }).Flatten2();
     }
 
     private async Task Save(
diff --git a/c#/imagePipeline/src/Consumer/HashConsumer.cs b/c#/imagePipeline/src/Consumer/HashConsumer.cs
index 1982f52b..7fe2235f 100644
--- a/c#/imagePipeline/src/Consumer/HashConsumer.cs
+++ b/c#/imagePipeline/src/Consumer/HashConsumer.cs
@@ -91,7 +91,7 @@ static byte[] GetThumbHashForMatrix(Mat mat)
             return rgbaMat.GetArray(out Vec4b[] pixels)
                 ? ThumbHashes.Utilities.RgbaToThumbHash(mat.Width, mat.Height, pixels
                     .Select(vec => new[] {vec.Item0, vec.Item1, vec.Item2, vec.Item3})
-                    .SelectMany(i => i).ToArray())
+                    .Flatten2().ToArray())
                 : throw new InvalidOperationException("Failed to convert matrix into byte array.");
         }
     };
diff --git a/c#/imagePipeline/src/Consumer/QrCodeConsumer.cs b/c#/imagePipeline/src/Consumer/QrCodeConsumer.cs
index 8ffd8a43..4f04de60 100644
--- a/c#/imagePipeline/src/Consumer/QrCodeConsumer.cs
+++ b/c#/imagePipeline/src/Consumer/QrCodeConsumer.cs
@@ -29,7 +29,7 @@ protected override IEnumerable<ImageId> ConsumeInternal(
                 imageKeyWithMatrix => imageKeyWithMatrix.ImageId,
                 ScanQrCodeInImage)
             .ToList();
-        db.ImageQrCodes.AddRange(imageQrCodeEithers.Rights().SelectMany(i => i));
+        db.ImageQrCodes.AddRange(imageQrCodeEithers.Rights().Flatten2());
         return imageQrCodeEithers.Lefts();
     }
 
diff --git a/c#/imagePipeline/src/ImageBatchConsumingWorker.cs b/c#/imagePipeline/src/ImageBatchConsumingWorker.cs
index 4e000833..a16def59 100644
--- a/c#/imagePipeline/src/ImageBatchConsumingWorker.cs
+++ b/c#/imagePipeline/src/ImageBatchConsumingWorker.cs
@@ -109,7 +109,7 @@ void ConsumeConsumer<TImage, TConsumer>(
                     .Where(i => i.ImageInReply is not {HashConsumed: true, QrCodeConsumed: true, OcrConsumed: true}),
                 imageWithBytes => imageWithBytes.ImageInReply.ImageId,
                 DecodeImageOrFramesBytes(stoppingToken))
-            .Rights().SelectMany(i => i).ToList();
+            .Rights().Flatten2().ToList();
         try
         {
             IReadOnlyCollection<ImageKeyWithMatrix> ExceptConsumed
@@ -200,7 +200,7 @@ private async Task ConsumeOcrConsumer(
         var scriptGroupings = await forumScripts.AsNoTracking()
             .GroupBy(e => e.Fid, e => e.Script)
             .ToListAsync(stoppingToken);
-        var scripts = scriptGroupings.SelectMany(i => i).Distinct().ToList();
+        var scripts = scriptGroupings.Flatten2().Distinct().ToList();
         var recognizedTextLinesKeyByScript = new Dictionary<string, List<ImageOcrLine>>(scripts.Count);
         scripts.ForEach(script => recognizedTextLinesKeyByScript[script] = []);
 
diff --git a/c#/imagePipeline/src/Ocr/JointRecognizer.cs b/c#/imagePipeline/src/Ocr/JointRecognizer.cs
index 92f39a4d..570f627d 100644
--- a/c#/imagePipeline/src/Ocr/JointRecognizer.cs
+++ b/c#/imagePipeline/src/Ocr/JointRecognizer.cs
@@ -42,10 +42,10 @@ public IReadOnlyCollection<Either<ImageId, IRecognitionResult>> RecognizeMatrice
         var detectedEithers = _paddleOcrProvider
             .DetectMatrices(matricesKeyByImageKey, failedImageHandler, stoppingToken).ToList();
         var recognizedResultsViaPaddleOcr =
-            recognizedEithersViaPaddleOcr.Rights().SelectMany(i => i).ToList();
+            recognizedEithersViaPaddleOcr.Rights().Flatten2().ToList();
         var recognizedEithersViaTesseract = RecognizeMatricesViaTesseract(
                 recognizedResultsViaPaddleOcr,
-                detectedEithers.Rights().SelectMany(i => i).ToList(),
+                detectedEithers.Rights().Flatten2().ToList(),
                 matricesKeyByImageKey,
                 stoppingToken)
             .ToList();
diff --git a/c#/shared/src/ExtensionMethods.cs b/c#/shared/src/ExtensionMethods.cs
index 6e44b3e1..e52d82f7 100644
--- a/c#/shared/src/ExtensionMethods.cs
+++ b/c#/shared/src/ExtensionMethods.cs
@@ -46,6 +46,9 @@ public static IEnumerable<KeyValuePair<TKey, TValue>> IntersectByKey<TKey, TValu
         this IEnumerable<KeyValuePair<TKey, TValue>> first,
         IEnumerable<TKey> second) =>
         first.IntersectBy(second, pair => pair.Key);
+
+    public static IEnumerable<T> Flatten2<T>(this IEnumerable<IEnumerable<T>> source) =>
+        source.SelectMany(i => i);
 }
 public static partial class ExtensionMethods
 {