migrate-nullable-references

SKILL.md

Nullable Reference Migration

Enable C# nullable reference types (NRTs) in an existing codebase and systematically resolve all warnings. The outcome is a project (or solution) with <Nullable>enable</Nullable>, zero nullable warnings, and accurately annotated public API surfaces — giving both the compiler and consumers reliable nullability information.

When to Use

Enabling nullable reference types in an existing C# project or solution

Systematically resolving CS86xx nullable warnings after enabling the feature

Annotating a library's public API surface so consumers get accurate nullability information

Upgrading a dependency that has added nullable annotations and new warnings appear

Analyzing suppressions in a code base that has already enabled NRTs to determine whether they can be removed

When Not to Use

The project already has <Nullable>enable</Nullable> and zero warnings — the migration is done unless the user wants to re-examine suppressions with a view to removing unnecessary ones (see Step 6)

The user only wants to suppress warnings without fixing them (recommend against this)

The code targets C# 7.3 or earlier, which does not support nullable reference types

Inputs