csharp-nullable-types

Null reference exceptions in C# can be prevented by enabling nullable reference types (C# 8.0+) and using nullable annotations to declare which variables can be null. Apply null checks, null-coalescing operators (??), and null-conditional access (?.) to safely handle potential null values before dereferencing.

Nullable value types (int?, struct?) wrap value types to allow null assignment with HasValue and Value properties. Nullable reference types enable compile-time warnings on reference types that might be null. Both use nullable annotations but operate differently: value types remain stack-allocated, reference types remain heap-allocated.

The null-coalescing operator (??) returns the left operand if it's not null, otherwise returns the right operand. Use it to provide default values: `string name = user?.Name ?? "Unknown";`. Chain multiple operators for fallback sequences and combine with null-conditional access (?.) for safe property navigation.

Yes. Apply nullable annotations to method parameters, return types, and properties to enforce null-safety checks at compile time. Mark nullable parameters and return types with ?, non-nullable without it. This propagates null expectations across your codebase, helping prevent null reference exceptions at call sites.

Nullable reference types are available in C# 8.0 and later. Enable them per-project or per-file using `#nullable enable`. Nullable value types (int?, struct?) have been available since C# 2.0, but the modern nullable reference type system requires C# 8.0+ for compile-time null-safety annotations.

Use null-conditional access with indexers and iterators: `list?[index]?.Property`. For nullable value types, check HasValue before accessing Value. Use LINQ methods like FirstOrDefault with null coalescing for safe retrieval from collections containing nullable elements.