null coalescing

The ?? operator returns the left operand if not null, otherwise the right. ??= assigns only if the variable is null.

Syntax

csharp

result = value ?? fallback;
variable ??= defaultValue;

Example

csharp

string name = user.Name ?? "Anonymous";
int count = GetCount() ?? 0;

// Null-conditional combined:
string city = user?.Address?.City ?? "Unknown";

// Null coalescing assignment:
_cache ??= new Dictionary<string, object>();