Nullable types and null safety — C# Language — Basics to Advanced

18. Nullable types and null safety

Intermediate★ Must knowLesson 18 of 38

csharp

int? maybe = null;                 // Nullable<int>
if (maybe.HasValue) Console.WriteLine(maybe.Value);
int value = maybe ?? -1;

#nullable enable                   // nullable reference types (C# 8) — on by default in new projects
string name = "x";                 // must not be null
string? middle = null;             // may be null
Console.WriteLine(middle?.Length); // compiler warns if you dereference without a check
string sure = middle!;             // null-forgiving operator — you promise it isn't null

Nullable reference types are compile-time warnings only; at runtime a string can still be null if a warning was ignored.