摘要： http://stackoverflow.com/questions/12424537/why-ienumerablet-is-defined-as-ienumerableout-t-not-ienumerabletThe out type parameter specifier denotes covariance.In practice,If I define two interfaces.ISomeInterface<T>{}ISomeCovariantInterface<out T>{}Then, I implement them like this.SomeC 阅读全文