Answer
Covariance: Allows using a more derived type than originally specified.
Contravariance: Allows using a more base type than originally specified.
Quick Answer
These control how generic types relate when type parameters have an inheritance relationship. Covariance (out T) lets you use IEnumerable where IEnumerable is expected — safe because you only read. Contravariance (in T) allows Action where Action is expected — safe because you only write.
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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