Editing C preprocessor (section)

=== Nullable ===
The <code>#nullable</code> directive in C# is used to enable and disable nullable reference types. To enable them, use <code>#nullable enable</code>, and <code>#nullable disable</code> to disable them. 

<syntaxhighlight lang="csharp">
#nullable enable

string? name = null; // OK
string fullName = null; // Warning: possible null assignment

#nullable disable

string test = null; // No warning
</syntaxhighlight>

This directive does not exist in C/C++.