Nullable annotation context

Context: The nullable annotation context is controlled by #nullable directives. It enables or disables nullable warnings and annotations.

Directives

#nullable enable   // Enables nullable annotations and warnings
#nullable disable  // Disables (default for legacy code)
#nullable restore  // Restores to project default
#nullable enable annotations  // Only annotations
#nullable enable warnings     // Only warnings

Project‑level setting

In .csproj:

<PropertyGroup>
  <Nullable>enable</Nullable>
</PropertyGroup>

Real-world usage example

Migrating legacy code: Use #nullable disable at the top of old files to temporarily disable warnings while you gradually enable nullable contexts.

Example: The .NET runtime itself migrated to nullable reference types file by file using this technique.

Related sections

• 6.4 Nullable reference types
• 6.4.4 Nullable warnings