And while IList isn't covariant, a read-only list interface would be.

即使IList接口不是协变的，一个只读列表接口也理应如此。

youdao

Using IList to model a set is unfortunate: it creates a semantic problem because lists allow duplicates.

使用IList来对set建模是让人徒呼奈何的一件事情：它会带来语义上的冲突，因为list允许出现重复的元素。

youdao

Perhaps the solution here is to retroactively create base classes for IList that separate the methods that accept a T value from the ones that return one.

或许这里应该针对IList创建一个基类，该类会将接受T与返回T的方法区分开来。

youdao