---
title: "C# Nullable Reference Types - Air Market"
description: "In C# it is easy to write code that assumes something is there when it might not be. This explains how to mark what can and cannot be missing so the compiler warns you first, and how to add those mar…"
canonical: "https://airmarket.ai/app/csharp-nullable-reference-types"
---

[Air Market](/) / [Developer Tools](/category/devtools) / C# Nullable Reference Types

Skill by [Aaron Stannard](/@aaronontheweb)

# C# Nullable Reference Types

Say what can be null and let the compiler hold you to it

## What this does

In C# it is easy to write code that assumes something is there when it might not be. This explains how to mark what can and cannot be missing so the compiler warns you first, and how to add those marks to an existing codebase gradually rather than all at once. Reach for it when null checks and warnings are getting confusing.

### Top 3 things it does for you

- Turn on nullable reference types without drowning in warnings
- Pick the right nullable attribute for this method
- Migrate an older codebase a piece at a time

## Information

**C# Nullable Reference Types at a glance**

|  |  |
| --- | --- |
| Kind | Skill |
| Publisher | [Aaron Stannard](/@aaronontheweb) |
| Category | [Developer Tools](/category/devtools) |
| Works with | Agent Skills - an open standard supported by 40+ agents |
| Version | 1.0.0 |
| Size | 40 KB |
| Licence | MIT |
| Repository | [Aaronontheweb/dotnet-skills](https://github.com/Aaronontheweb/dotnet-skills/tree/13e26d39ed01d97ea592235d041304d289f4ba07/skills/csharp-nullable-reference-types) |
| GitHub stars | 1,123 (as of Nov 2026) |

## Security report

**Verified.** AIR scanned this exact version of C# Nullable Reference Types and flagged nothing. AIR's verdict: **safe**.

**What C# Nullable Reference Types's check was run against**

|  |  |
| --- | --- |
| Commit | 13e26d39ed01d97ea592235d041304d289f4ba07 |
| Content hash | 6d8c2a542cd8371056f334fe7d85176d51787bf5aae3467a25162a209c87810e |
| Files read | [Browse the files at this exact commit](https://github.com/Aaronontheweb/dotnet-skills/blob/13e26d39ed01d97ea592235d041304d289f4ba07/skills/csharp-nullable-reference-types/SKILL.md) |

A scan is named by the exact content it read, not by a version number. A different version is a different artifact, and nothing here applies to a version AIR has not scanned.

[Read the full security report for C# Nullable Reference Types](/security/csharp-nullable-reference-types)

## About C# Nullable Reference Types

Nullable reference types change how the compiler reads your code, and the details matter: how the nullability model works, how flow analysis tracks what it knows, and when the null-forgiving operator is the right escape hatch rather than a way to quiet a real problem.

The skill covers the full attribute catalog from System.Diagnostics.CodeAnalysis - AllowNull, DisallowNull, MaybeNull, NotNull, NotNullWhen, MaybeNullWhen, NotNullIfNotNull, MemberNotNull, MemberNotNullWhen, DoesNotReturn and DoesNotReturnIf - along with rules for designing APIs whose signatures tell the truth.

It also handles the practical side: the C# 14 field keyword, incremental migration of legacy codebases, and a checklist for generated code.

## What's inside

- SKILL.md - instructions
- nrt-migration-playbook-reference.md - reference
- nullable-attributes-reference.md - reference

## Questions

### Is C# Nullable Reference Types safe to install?

AIR scanned this exact version of C# Nullable Reference Types and flagged nothing. AIR's verdict: safe. The verdict is named by the content that was read, at commit 13e26d39ed01, so it cannot drift onto a version nobody scanned. The full report is at https://airmarket.ai/security/csharp-nullable-reference-types.

### How do I install C# Nullable Reference Types?

Open https://airmarket.ai/app/csharp-nullable-reference-types on Air Market and use the install action: Air Market hands Claude a prompt naming this exact skill, and Claude sets it up. Source, pinned to the exact commit this listing describes: https://github.com/Aaronontheweb/dotnet-skills/tree/13e26d39ed01d97ea592235d041304d289f4ba07/skills/csharp-nullable-reference-types. Install from that link, not the branch.

## Related on Air Market

- [More Developer Tools listings](/category/devtools)
- [Everything by Aaron Stannard](/@aaronontheweb)

---

Canonical URL: <https://airmarket.ai/app/csharp-nullable-reference-types>