nullable-attributes

name	nullable-attributes
description	Apply C# nullable analysis attributes from System.Diagnostics.CodeAnalysis when `?`, non-nullable declarations, and ordinary flow analysis are not enough. Use for Try-patterns, guard helpers, late initialization, member null-state guarantees, generic nullability, and compiler flow hints around nullable warnings.

Nullable attributes

When to Use

• The compiler reports a nullable warning that cannot be resolved with ? annotations and ordinary control flow.
• A TryGet or predicate method guarantees non-null on success but the compiler cannot infer that.
• A guard helper always throws on null, so code after the call is definitively non-null.
• A member is initialized by a helper method rather than the constructor, and the compiler treats it as possibly null.
• A generic method returns default on failure without changing value-type signatures.

When Not to Use

• The contract can be expressed with plain ? annotations and straightforward guard clauses.
• You are using the attribute to silence a warning without genuine evidence of the contract.
• The attribute would describe a different null contract than the actual behavior.

Inputs

Input	Required	Description
Method or member with nullable warning	Yes	The exact API position where the contract is unclear to the compiler
Intended null contract	Yes	Whether the value is guaranteed non-null, may be null, or depends on a return value

Load ../../../docs/ai-skills/nullable-attributes/references/nullable-attributes.md for the attribute table and selection notes.

Workflow

1. Prefer plain type annotations and ordinary guards first.
2. Add nullable attributes only for contracts the compiler cannot infer.
3. Keep the change metadata-only unless behavior changes were explicitly requested.
4. Pick the narrowest attribute that matches the contract.

Validation

• The attribute is applied to a position where the compiler actually uses it.
• The declared null contract matches real behavior.
• Nullable warnings are reduced without hiding bugs behind fake suppressions.