Hi All I'm very confused about this issue and can't to underestand it.In the Enumerable Documentation, I readed this: that implement System.Collections.Generic.IEnumerable and some methods like Select() return IEnumerable that we can use from other methods like Where() after using that.for example: names.Select(name => name).Where(name => name.Length > 3 ); but Enumerable doesn't inherits from IEnumerable and IEnumerable doesn't contain Select(),Where() and etc too... have i wrong ? or exists any reason for this?