Answer
Covariance (out) allows substituting derived for base. Contravariance (in) allows substituting base for derived. Applies to delegates, interfaces, and arrays (with runtime checks). Enables type-flexible APIs safely.
Quick Answer
Covariance (out T on IEnumerable): IEnumerable is assignable to IEnumerable — safe for read-only scenarios. Contravariance (in T on Action): Action is assignable to Action — safe for write-only scenarios. Applies to interfaces and delegates, not concrete classes. The in/out keywords express the variance direction.
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SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
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Source: SugharaIQ