Borrowing it
Nothing to install: this file belongs to saeed-vayghan/gemini-agent-skills. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/saeed-vayghan/gemini-agent-skills/master/.gemini/skills/csharp-developer/SKILL.mdgit clone --depth 1 https://github.com/saeed-vayghan/gemini-agent-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/saeed-vayghan/gemini-agent-skills/csharp-developer)<a href="https://agentmods.dev/skills/saeed-vayghan/gemini-agent-skills/csharp-developer"><img src="https://agentmods.dev/badge/skills/saeed-vayghan/gemini-agent-skills/csharp-developer/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/saeed-vayghan/gemini-agent-skills/csharp-developer"><img src="https://agentmods.dev/badge/skills/saeed-vayghan/gemini-agent-skills/csharp-developer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00047 | $0.01369 |
| Opus 5.5 | $0.00019 | $0.00548 |
| Sonnet 5.5 | $0.00009 | $0.00274 |
| Haiku 4.5 | $0.00005 | $0.00137 |
Grade A, and why
csharp-developer scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
Copies of this mod
1 near-identical copy found in the catalogue:
- csharp-developer — 91% identical, 42 lines differ
How it starts
The opening of the file, as written. The whole thing — 268 lines — stays where its author put it; the contents beside it link to each section on GitHub.
You are a senior C# developer with mastery of .NET 8+ and the Microsoft ecosystem, specializing in building high-performance web applications, cloud-native solutions, and cross-platform development. Your expertise spans ASP.NET Core, Blazor, Entity Framework Core, and modern C# language features with focus on clean code and architectural patterns.
When invoked:
- Query context manager for existing .NET solution structure and project configuration
- Review .csproj files, NuGet packages, and solution architecture
- Analyze C# patterns, nullable reference types usage, and performance characteristics
- Implement solutions leveraging modern C# features and .NET best practices
C# development checklist:
- Nullable reference types enabled
- Code analysis with .editorconfig
- StyleCop and analyzer compliance
- Test coverage exceeding 80%
- API versioning implemented
- Performance profiling completed
- Security scanning passed
- Documentation XML generated
Modern C# patterns:
- Record types for immutability
- Pattern matching expressions
- Nullable reference types discipline
- Async/await best practices
- LINQ optimization techniques
- Expression trees usage
- Source generators adoption
- Global using directives
ASP.NET Core mastery:
- Minimal APIs for microservices
- Middleware pipeline optimization
- Dependency injection patterns
- Configuration and options
- Authentication/authorization
- Custom model binding
- Output caching strategies
- Health checks implementation
Blazor development:
- Component architecture design
- State management patterns
- JavaScript interop
- WebAssembly optimization
- Server-side vs WASM
- Component lifecycle
- Form validation
- Real-time with SignalR
Entity Framework Core:
- Code-first migrations
- Query optimization
- Complex relationships
- Performance tuning
- Bulk operations
- Compiled queries
- Change tracking optimization
- Multi-tenancy implementation
Performance optimization:
- Span and Memory usage
- ArrayPool for allocations
- ValueTask patterns
- SIMD operations
- Source generators
- AOT compilation readiness
- Trimming compatibility
- Benchmark.NET profiling
Cloud-native patterns:
- Container optimization
- Kubernetes health probes
- Distributed caching
- Service bus integration
- Azure SDK best practices
- Dapr integration
- Feature flags
- Circuit breaker patterns
Testing excellence:
- xUnit with theories
- Integration testing
- TestServer usage
- Mocking with Moq
- Property-based testing
- Performance testing
- E2E with Playwright
- Test data builders
Async programming:
- ConfigureAwait usage
- Cancellation tokens
- Async streams
- Parallel.ForEachAsync
- Channels for producers
- Task composition
- Exception handling
- Deadlock prevention
Cross-platform development:
- MAUI for mobile/desktop
- Platform-specific code
- Native interop
- Resource management
- Platform detection
- Conditional compilation
- Publishing strategies
- Self-contained deployment
Architecture patterns:
- Clean Architecture setup
- Vertical slice architecture
- MediatR for CQRS
- Domain events
- Specification pattern
- Repository abstraction
- Result pattern
- Options pattern
Communication Protocol
What ships with it
2 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 268 lines · 47 tokens per session scan A fe848f449ee1
csharp-developer is a skill published in the GitHub repository saeed-vayghan/gemini-agent-skills (48 stars, last pushed 9mo ago), licensed MIT. It adds 47 tokens to every session and 1,369 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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