Question

What is the correct syntax for this:

IList<string> names = 'Tom,Scott,Bob'.Split(',').ToList<string>().Reverse(); 

What am I messing up? What does TSource mean?

Answer 1

The problem is that you’re calling List<T>.Reverse() which returns void.

You could either do:

List<string> names = 'Tom,Scott,Bob'.Split(',').ToList<string>(); names.Reverse(); 

or:

IList<string> names = 'Tom,Scott,Bob'.Split(',').Reverse().ToList<string>(); 

The latter is more expensive, as reversing an arbitrary IEnumerable<T> involves buffering all of the data and then yielding it all – whereas List<T> can do all the reversing ‘in-place’. (The difference here is that it’s calling the Enumerable.Reverse<T>() extension method, instead of the List<T>.Reverse() instance method.)

More efficient yet, you could use:

string[] namesArray = 'Tom,Scott,Bob'.Split(','); List<string> namesList = new List<string>(namesArray.Length); namesList.AddRange(namesArray); namesList.Reverse(); 

This avoids creating any buffers of an inappropriate size – at the cost of taking four statements where one will do… As ever, weigh up readability against performance in the real use case.