Shorter syntax for casting from a List<X> to a List<Y>?

Question

I know its possible to cast a list of items from one type to another (given that your object has a public static explicit operator method to do the casting) one at a time as follows:

List<Y> ListOfY = new List<Y>();

foreach(X x in ListOfX)
    ListOfY.Add((Y)x);

But is it not possible to cast the entire list at one time? For example,

ListOfY = (List<Y>)ListOfX;

Answer 1

If X can really be cast to Y you should be able to use

List<Y> listOfY = listOfX.Cast<Y>().ToList();

Some things to be aware of (H/T to commenters!)

• You must include using System.Linq; to get this extension method
• This casts each item in the list - not the list itself. A new List<Y> will be created by the call to ToList().
• This method does not support custom conversion operators. ( see http://stackoverflow.com/questions/14523530/why-does-the-linq-cast-helper-not-work-with-the-implicit-cast-operator )
• This method does not work for an object that has a explicit operator method (framework 4.0)