By 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
TryGetor 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
defaulton 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
- Prefer plain type annotations and ordinary guards first.
- Add nullable attributes only for contracts the compiler cannot infer.
- Keep the change metadata-only unless behavior changes were explicitly requested.
- 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.