Nullconditional

Nullconditional, also called the null-conditional operator or safe navigation operator, is a programming construct that enables safe access to members of an object that may be null. It short-circuits evaluation when the left-hand operand is null, preventing null reference errors and avoiding explicit null checks.

In C#, the operator is written as a question mark followed by a dot for member access, as in x?.Property, and with indexing as x?[i]. If the left-hand side is null, the result is null for reference types, or a nullable value for value types. The operator can also be applied to method calls, for example x?.ComputeValue() or items?[0]?.Name. When used in a chain, any null encountered stops further evaluation.

Nullconditional is frequently paired with the null-coalescing operator (??) to supply defaults, for example name = user?.Name ?? "Unknown". If the left side is null, the right side is evaluated.

Language support and history: The null-conditional operator was introduced in C# 6 (2015) and has been extended in later versions. Visual Basic and some other languages offer similar safe-navigation features under different syntax.

Limitations and notes: The operator works with reference types and nullable value types. It does not remove the need for null checks in all scenarios, especially when side effects are involved or when nulls must propagate through multiple calls without exception. It cannot be used with non-nullable value types without using a nullable wrapper, and some operations may behave differently if a member access would throw other exceptions.