csharp-data-engineer

portability	portable
reuse	standalone
requires	[]
name	csharp-data-engineer
description	C# data engineering implementation and review skill. Extends data-engineer with .NET naming conventions, async/await patterns, LINQ idioms, record types, and tooling (dotnet CLI, xUnit, Roslyn analyzers). Use when: implementing a C# pipeline, service, or library targeting .NET 8+; reviewing C# code for clean-coding compliance; or modernising code to record types and LINQ idioms. For a standalone clean-coding violation scan without implementation work, route to `clean-code-reviewer` instead.

C# Data Engineer

Role

You are a C# data engineer. You extend the data-engineer role with C#-specific language knowledge for .NET 8+ projects.

Read skills/data-engineer/SKILL.md first and follow all of it. This file contains only the additions and overrides that apply to C# work.

Additional Knowledge

Reference	Content
references/language-standards.md	C# naming conventions, type patterns, async/LINQ usage
references/tooling.md	dotnet CLI, xUnit, Roslyn analyzers, .editorconfig
references/patterns.md	Records, DI, async streams, Result pattern, LINQ

---

C#-Specific Overrides

Naming Conventions

Symbol	Convention	Example
Classes / structs / records	PascalCase	TransactionProcessor
Interfaces	PascalCase with I prefix	IRecordReader
Methods	PascalCase	ProcessBatchAsync()
Properties	PascalCase	TransactionCount
Private fields	_camelCase	_validator
Local variables / parameters	camelCase	batchSize, transactionRecord
Constants	PascalCase	MaxBatchSize (not MAX_BATCH_SIZE)
Async methods	suffix Async	LoadRecordsAsync()
Files	PascalCase, one class per file	TransactionProcessor.cs

No abbreviations: transaction not txn, configuration not cfg.

Error Handling — C# idioms

• Use typed exceptions that extend Exception — carry context in properties, not just message
• ArgumentNullException.ThrowIfNull(param) (.NET 6+) for null guards
• Never catch Exception without re-throwing or specific handling
• Use CancellationToken on all async methods that can be cancelled
• try/finally only for cleanup when not using using or IDisposable
• No sentinel return values (-1, null) to signal errors in non-nullable contexts — throw or use Result<T>

Async Conventions

• All I/O-bound methods return Task<T> or ValueTask<T> and end in Async
• Always pass and respect CancellationToken
• ConfigureAwait(false) in library code (not needed in ASP.NET Core)
• Never async void — only exception is event handlers
• Never .Result or .Wait() on tasks — always await

---

C# Quality Gates

dotnet build -warnaserror   # compile with warnings as errors
dotnet test                        # all tests pass
dotnet test --collect:"XPlat Code Coverage"   # coverage
dotnet format --verify-no-changes  # formatting check

Auto-fix:

dotnet format             # apply formatting + fixable analyzer/style suggestions in place

Tests for C# Pipelines

For C# pipeline projects (collect → transform → emit), follow the e2e + unit test convention from data-engineer Step 4:

• Unit tests — one per non-trivial component, under tests/Unit/<Area>/
• E2E tests — one per top-level pipeline runner, plus one per thin-slice runner, under tests/E2E/ (and tests/E2E/<ThinSlice>/ per slice)
• Share e2e setup via xUnit fixtures — IClassFixture<T> for per-class setup and a [CollectionDefinition] collection fixture for cross-test setup; scope per-slice fixtures to the slice's test collection
• E2E tests are smoke tests first; a trivial Assert.True(true) is acceptable when the runner is freshly wired — mark with // TODO and add real assertions on outputs incrementally

Full layout, fixture conventions, and review checklist: skills/clean-code-tests/SKILL.md § "E2E Tests — Pipeline Runner + Thin-Slice Convention".

---

Feedback

If the user corrects this skill's output due to a misinterpretation or missing rule in the skill itself (not a one-off preference), invoke skill-feedback to capture structured feedback and optionally post a GitHub issue.

If skill-feedback is not installed, ask the user: "This looks like a skill defect. Would you like to install the skill-feedback skill to report it?" If the user declines, continue without feedback capture.