What is mcaf-dotnet-features?

Guidance for writing C# code that matches the language version and .NET framework used by a repository.

Checking whether C# 13 or C# 14 features are safe, choosing compatible syntax, and reviewing or upgrading language-feature use.

It prevents newer C# features from being used where the project cannot compile or support them.

mcaf-dotnet-features — Skill by managedcode

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods

npx agentmods add skills/managedcode/mcpgateway/mcaf-dotnet-features

Any agent

npx skills add managedcode/MCPGateway --skill mcaf-dotnet-features

Clone the repo

git clone --depth 1 https://github.com/managedcode/MCPGateway

Made for: Claude Code, Codex.

Per session 54 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.

When invoked 1,183 The whole file, excluding the scripts and references it only reads on demand.

Security scan A 0 findings. Scan, not verified.

Origin 95% copy Near-identical to another mod in the catalogue.

Token cost

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	$0.00054	$0.01183
Opus 5	$0.00027	$0.00592
Sonnet 5	$0.00011	$0.00237
Haiku 4.5	$0.00005	$0.00118

Measured yesterday against content hash 7e8e6c71f68b, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

mcaf-dotnet-features 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 yesterday.

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.

Origin

This is a copy

95% identical to dotnet-modern-csharp — 16 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.

.codex/skills/mcaf-dotnet-features/SKILL.md · 118 lines

How it starts

The opening of the file, as written. The whole thing — 118 lines — stays where its author put it; the contents beside it link to each section on GitHub.

MCAF: .NET Features

Trigger On

the repo wants more modern idiomatic C# code
a change depends on language-version compatibility
the team is upgrading or reviewing C# feature usage across versions
you need to know whether a C# 13 or C# 14 feature is safe to use

Value

produce a concrete project delta: code, docs, config, tests, CI, or review artifact
reduce ambiguity through explicit planning, verification, and final validation skills
leave reusable project context so future tasks are faster and safer

Do Not Use For

non-C# .NET languages such as F# or VB
analyzer-only or formatter-only setup with no language feature choice

Inputs

target TFM or TFMs
explicit LangVersion, if any
current SDK version
team style rules in .editorconfig and AGENTS.md

Quick Start

Read the nearest AGENTS.md and confirm scope and constraints.
Run this skill's Workflow through the Ralph Loop until outcomes are acceptable.
Return the Required Result Format with concrete artifacts and verification evidence.

Workflow

Detect the real language ceiling from the repo's target framework and explicit LangVersion.
Prefer stable features that the current repo actually supports.
Use modern syntax when it reduces ceremony, improves correctness, or makes invariants clearer.
Do not mass-rewrite a codebase into newer syntax unless the repo wants that churn.
Treat preview features as opt-in only. Never assume preview because the current machine has a newer SDK.
Pay special attention to C# 13 and C# 14:
- C# 13 is the stable language for .NET 9
- C# 14 is the stable language for .NET 10
When feature selection changes architecture, style rules, or generated-code patterns, coordinate with:
- mcaf-dotnet
- mcaf-dotnet-analyzer-config
- mcaf-solid-maintainability
After feature-driven refactors, run the repo's .NET quality pass through mcaf-dotnet.

Bootstrap When Missing

If the requested C# feature depends on SDK or language support the repo does not have yet:

Read the full file on GitHub · 118 lines

Files

What ships with it

1 file 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.

references/csharp-modern-features.md 5.6 KB

Changes

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.

yesterday First seen · 118 lines · 54 tokens per session scan A 7e8e6c71f68b

Subscribe to this mod's changes

mcaf-dotnet-features is a skill published in the GitHub repository managedcode/MCPGateway (5 stars, last pushed 2d ago), licensed MIT. It adds 54 tokens to every session and 1,183 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. It is 95% identical to dotnet-modern-csharp, differing in 16 lines, and is treated as a copy.

Research Writing and docs ai-extensions csharp dotnet embeddings mcp mcp-gateway

mcaf-dotnet-features