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variance

Whether a generic type can stand in for a related one, like IEnumerable for IEnumerable.

Covariance (out) and contravariance (in) on interface and delegate type parameters allow implicit reference conversions between constructed types.

Examples

  • IEnumerable<object> items = words; works when words is an IEnumerable<string>; the same with List<object> and List<string> is error CS0029.

See also

generic type IEnumerable<T> delegate
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