dotnet-guide-com · balajibashyam · Aug 5, 2026 · Aug 5, 2026 · Aug 5, 2026 · Aug 5, 2026
diff --git a/.github/workflows/build-samples.yml b/.github/workflows/build-samples.yml
@@ -22,6 +22,7 @@ on:
       - "cloud-native/polly-resilience/**"
       - "csharp-language/csharp-12-features/**"
       - "csharp-language/high-performance-memory-management/**"
+      - "csharp-language/modern-patterns-result-pipeline/**"
       - ".github/workflows/build-samples.yml"
 
   pull_request:
@@ -44,6 +45,7 @@ on:
       - "cloud-native/polly-resilience/**"
       - "csharp-language/csharp-12-features/**"
       - "csharp-language/high-performance-memory-management/**"
+      - "csharp-language/modern-patterns-result-pipeline/**"
       - ".github/workflows/build-samples.yml"
 
   workflow_dispatch:
@@ -894,3 +896,100 @@ jobs:
           )"
 
           test "${line_count}" = "6"
+
+  test-result-pipeline:
+    name: Test C# Result pipeline sample
+    runs-on: ubuntu-latest
+
+    permissions:
+      contents: read
+
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v5
+
+      - name: Install .NET 10 SDK
+        uses: actions/setup-dotnet@v5
+        with:
+          dotnet-version: "10.0.x"
+
+      - name: Restore
+        run: >
+          dotnet restore
+          csharp-language/modern-patterns-result-pipeline/ResultPipelineLab.slnx
+
+      - name: Build
+        run: >
+          dotnet build
+          csharp-language/modern-patterns-result-pipeline/ResultPipelineLab.slnx
+          --configuration Release
+          --no-restore
+
+      - name: Test
+        run: >
+          dotnet test
+          csharp-language/modern-patterns-result-pipeline/ResultPipelineLab.slnx
+          --configuration Release
+          --no-build
+
+      - name: Verify explicit C# language version
+        shell: bash
+        run: |
+          app_version="$(
+            dotnet msbuild \
+              csharp-language/modern-patterns-result-pipeline/src/ResultPipelineLab/ResultPipelineLab.csproj \
+              -getProperty:LangVersion
+          )"
+
+          test_version="$(
+            dotnet msbuild \
+              csharp-language/modern-patterns-result-pipeline/tests/ResultPipelineLab.Tests/ResultPipelineLab.Tests.csproj \
+              -getProperty:LangVersion
+          )"
+
+          echo "Application LangVersion: ${app_version}"
+          echo "Test LangVersion: ${test_version}"
+
+          test "${app_version}" = "12.0"
+          test "${test_version}" = "12.0"
+
+      - name: Run deterministic Result pipeline sample
+        shell: bash
+        run: |
+          output="$(
+            dotnet run \
+              --project csharp-language/modern-patterns-result-pipeline/src/ResultPipelineLab/ResultPipelineLab.csproj \
+              --configuration Release \
+              --no-build
+          )"
+
+          printf '%s\n' "${output}"
+
+          printf -v expected '%s\n' \
+            'C# 12 Result Pipeline Lab' \
+            'Success: imported=2, writes=1' \
+            'Products: Widget Pro | Travel Mug' \
+            'Failure: code=VALIDATE_BATCH_FAILED, writes=0' \
+            'Public message: 1 record(s) failed validation.'
+
+          expected="${expected%$'\n'}"
+
+          if [[ "${output}" != "${expected}" ]]; then
+            echo "Console output did not match the expected output."
+
+            diff \
+              --unified \
+              <(printf '%s\n' "${expected}") \
+              <(printf '%s\n' "${output}") \
+              || true
+
+            exit 1
+          fi
+
+          line_count="$(
+            printf '%s\n' "${output}" |
+              wc --lines |
+              tr --delete ' '
+          )"
+
+          test "${line_count}" = "5"
diff --git a/README.md b/README.md
@@ -27,6 +27,7 @@ Each sample folder contains a focused implementation of one tutorial topic. The
 | [`cloud-native/polly-resilience`](cloud-native/polly-resilience/) | Focused .NET 10 Polly v8 catalog sample demonstrating explicit stale-cache fallback, timeout-driven degradation, outbound concurrency isolation, strategy event counters, and deterministic integration testing | [Polly Resilience (Polly v8): Timeouts, Retries, Circuits, Bulkheads, Hedging](https://www.dotnet-guide.com/tutorials/cloud-native/polly-resilience/) |
 | [`csharp-language/csharp-12-features`](csharp-language/csharp-12-features/) | Focused .NET 10 console lab locked to C# 12.0, demonstrating primary constructors with explicit properties, collection expressions and spreads, default lambda parameters, tuple-type aliases, deterministic output, and unit tests | [C# 12 Language Features: Primary Constructors, Collections & More](https://www.dotnet-guide.com/tutorials/csharp-language/csharp-12-features/) |
 | [`csharp-language/high-performance-memory-management`](csharp-language/high-performance-memory-management/) | Focused .NET 10 UTF-8 ingestion sample demonstrating PipeReader framing, segmented ReadOnlySequence handling, span-based numeric parsing, bounded MemoryPool ownership, strict input validation, deterministic output, and tests | [High-Performance C#: Span<T>, Memory<T>, SIMD & Pipelines](https://www.dotnet-guide.com/tutorials/csharp-language/high-performance-memory-management/) |
+| [`csharp-language/modern-patterns-result-pipeline`](csharp-language/modern-patterns-result-pipeline/) | Focused .NET 10 console companion locked to C# 12.0, demonstrating a custom Result type, safe and diagnostic errors, Map/Bind/BindAsync composition, invariant text-import validation, short-circuit persistence, cancellation, deterministic output, and tests | [C# 12 Functional Patterns: Result Type, Error Handling & Composable Pipeline Testing](https://www.dotnet-guide.com/tutorials/csharp-language/modern-patterns-result-pipeline/) |
 
 ## Companion articles
 - [Common Microsoft.Extensions.AI mistakes](https://www.dotnet-guide.com/articles/dotnet-ai/microsoft-extensions-ai-common-mistakes/)
@@ -309,6 +310,29 @@ tutorials/
 |   |           `-- TestSupport/
 |   |               |-- ChunkedReadStream.cs
 |   |               `-- SegmentedSequence.cs
+|   |-- modern-patterns-result-pipeline/
+|   |   |-- ResultPipelineLab.slnx
+|   |   |-- README.md
+|   |   |-- src/
+|   |   |   `-- ResultPipelineLab/
+|   |   |       |-- ResultPipelineLab.csproj
+|   |   |       |-- Program.cs
+|   |   |       |-- Core/
+|   |   |       |   |-- Result.cs
+|   |   |       |   `-- ResultExtensions.cs
+|   |   |       |-- Models/
+|   |   |       |   `-- ImportModels.cs
+|   |   |       |-- Persistence/
+|   |   |       |   `-- InMemoryProductStore.cs
+|   |   |       `-- Pipeline/
+|   |   |           |-- ImportPipeline.cs
+|   |   |           |-- ParseStage.cs
+|   |   |           |-- TransformStage.cs
+|   |   |           `-- ValidateStage.cs
+|   |   `-- tests/
+|   |       `-- ResultPipelineLab.Tests/
+|   |           |-- ResultPipelineLab.Tests.csproj
+|   |           `-- ResultPipelineTests.cs
 |-- aspnet-core/
 |   |-- api-security-in-practice/
 |   |   |-- ApiSecurityMinimal.slnx

diff --git a/csharp-language/modern-patterns-result-pipeline/README.md b/csharp-language/modern-patterns-result-pipeline/README.md
@@ -0,0 +1,212 @@
+# C# 12 Result Pipeline Lab
+
+A focused .NET 10 console companion demonstrating typed expected failures,
+`Map`, `Bind`, `Match`, one async persistence boundary, invariant validation,
+safe error projection, short-circuit behavior, cancellation, deterministic
+output, and tests.
+
+## Full tutorial
+
+[C# 12 Functional Patterns: Result Type, Error Handling & Composable Pipeline Testing](https://www.dotnet-guide.com/tutorials/csharp-language/modern-patterns-result-pipeline/)
+
+## Framework and language note
+
+The tutorial is written for C# 12 with the .NET 8 generation.
+
+This companion targets .NET 10 because that is the DOTNET GUIDE repository's
+current SDK, but both projects explicitly set:
+
+```xml
+<LangVersion>12.0</LangVersion>
+```
+
+The sample uses an explicit fallback arm in every switch expression over
+`Result<T>`.
+
+C# 12 does not infer a closed hierarchy merely because the base constructor is
+private and the known cases are nested and sealed.
+
+## Pipeline
+
+```text
+restricted text
+  -> Parse
+  -> Bind Validate
+  -> Map Transform
+  -> BindAsync Persist
+  -> Match at the edge
+```
+
+Expected parse, validation, and configured storage failures are returned as
+`Result<T>.Failure`.
+
+Caller cancellation and programming defects remain exceptions.
+
+## Input format
+
+```text
+Name,Price,Category,Stock
+Widget Pro,9.99,Electronics,50
+```
+
+This is a deliberately restricted comma-delimited format.
+
+It does not support:
+
+- quoted fields;
+- commas inside values;
+- escaped quotes;
+- embedded newlines;
+- locale-specific decimal separators.
+
+Use a reviewed CSV library when those capabilities are required.
+
+## Error projection
+
+`PipelineError` contains:
+
+```text
+Code
+Message
+Detail
+```
+
+`ToPublic()` returns only:
+
+```text
+Code
+Message
+```
+
+`ToDiagnostic(stage)` includes internal detail.
+
+The existence of two projections does not automatically make debug detail safe.
+
+Do not serialize or ship diagnostic detail to external consumers without a
+reviewed redaction and sink policy.
+
+## Map and Bind
+
+Use `Map` when validated input is transformed without an expected failure
+result.
+
+Use `Bind` when the next stage returns its own `Result`.
+
+Use `BindAsync` to connect the prepared synchronous result to the asynchronous
+persistence boundary.
+
+The callbacks can still throw programming exceptions.
+
+## Validation
+
+Numeric values are parsed with `CultureInfo.InvariantCulture`.
+
+Parsed values are carried forward in `ValidatedProduct`, so transformation does
+not parse the same text again.
+
+All invalid rows are collected into internal detail.
+
+This sample is fail-whole-batch, not partial-success import.
+
+## Persistence
+
+The in-memory store has an asynchronous-shaped API for composition.
+
+It supports:
+
+- deterministic success;
+- deterministic expected rejection;
+- cancellation.
+
+It is not a database simulation or throughput benchmark.
+
+## Prerequisite
+
+- .NET 10 SDK
+
+## Restore, build, test, and run
+
+```powershell
+dotnet restore `
+  .\ResultPipelineLab.slnx
+
+dotnet build `
+  .\ResultPipelineLab.slnx `
+  --configuration Release `
+  --no-restore
+
+dotnet test `
+  .\ResultPipelineLab.slnx `
+  --configuration Release `
+  --no-build
+
+dotnet run `
+  --project .\src\ResultPipelineLab\ResultPipelineLab.csproj `
+  --configuration Release `
+  --no-build
+```
+
+## Expected output
+
+```text
+C# 12 Result Pipeline Lab
+Success: imported=2, writes=1
+Products: Widget Pro | Travel Mug
+Failure: code=VALIDATE_BATCH_FAILED, writes=0
+Public message: 1 record(s) failed validation.
+```
+
+## Project structure
+
+```text
+ResultPipelineLab.slnx
+README.md
+src/
+`-- ResultPipelineLab/
+    |-- ResultPipelineLab.csproj
+    |-- Program.cs
+    |-- Core/
+    |   |-- Result.cs
+    |   `-- ResultExtensions.cs
+    |-- Models/
+    |   `-- ImportModels.cs
+    |-- Persistence/
+    |   `-- InMemoryProductStore.cs
+    `-- Pipeline/
+        |-- ImportPipeline.cs
+        |-- ParseStage.cs
+        |-- TransformStage.cs
+        `-- ValidateStage.cs
+tests/
+`-- ResultPipelineLab.Tests/
+    |-- ResultPipelineLab.Tests.csproj
+    `-- ResultPipelineTests.cs
+```
+
+## Deliberately omitted
+
+- third-party Result packages;
+- FluentAssertions;
+- structured logging providers;
+- databases;
+- ASP.NET Core;
+- file uploads;
+- full CSV behavior;
+- partial success;
+- retries;
+- exception swallowing.
+
+## Verification
+
+- Companion target framework: .NET 10
+- Explicit language version: C# 12.0
+- Application NuGet dependencies: none
+- External services required: none
+- Expected tests: 10
+- Expected console lines: 5
+- Last reviewed: 2026-08-05
+
+This sample teaches composition and failure semantics. A production Result
+abstraction requires decisions about nullability, equality, error accumulation,
+serialization, observability, cancellation, exception translation, API
+contracts, and team conventions.
diff --git a/csharp-language/modern-patterns-result-pipeline/ResultPipelineLab.slnx b/csharp-language/modern-patterns-result-pipeline/ResultPipelineLab.slnx
@@ -0,0 +1,8 @@
+<Solution>
+  <Folder Name="/src/">
+    <Project Path="src/ResultPipelineLab/ResultPipelineLab.csproj" />
+  </Folder>
+  <Folder Name="/tests/">
+    <Project Path="tests/ResultPipelineLab.Tests/ResultPipelineLab.Tests.csproj" />
+  </Folder>
+</Solution>