dotnet-csharp-nullable-reference-types

To enable nullable reference types (NRT) in a C# project, add the <Nullable>enable</Nullable> property to your project file. This allows the compiler to perform null-state analysis and warn you about potential null reference exceptions.

The best way to migrate a legacy codebase to nullable reference types is to use an incremental, step-by-step strategy. This Skill provides migration guidance that helps you progressively enable NRT across large projects without breaking existing functionality.

You should use attributes like [NotNullWhen] and [MemberNotNull] in C# to define precise nullability contracts. They inform the compiler's null-state analysis about method behaviors, preventing false warnings and ensuring robust null checking.

Null state warnings after enabling nullable reference types usually occur because the compiler detects potential null values. Common pitfalls include ignoring compiler warnings or incorrectly using the null-forgiving operator (!) to suppress them instead of fixing the underlying null issue.

Yes, you can enable nullable reference types on a per-file basis in C#. While adding <Nullable>enable</Nullable> to your project file applies it project-wide, you can also use directives within individual files to control NRT annotations locally.

A common mistake when using the null-forgiving operator (!) in C# is applying it to silence compiler warnings without actually verifying null safety. This defeats the purpose of nullable reference types and can hide potential null reference exceptions in your code.