C# Syntax - Split String into Array by Comma, Convert To Generic List, and Reverse Order

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.

Answer 2

I realize that this question is quite old, but I had a similar problem, except my string had spaces included in it. For those that need to know how to separate a string with more than just commas:

string str = "Tom, Scott, Bob";
  IList<string> names = str.Split(new string[] {","," "},
  StringSplitOptions.RemoveEmptyEntries);

The StringSplitOptions removes the records that would only be a space char...

Answer 3

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

This one works.

Answer 4

Try this:

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

Answer 5

What your missing here is that .Reverse() is a void method. It's not possible to assign the result of .Reverse() to a variable. You can however alter the order to use Enumerable.Reverse() and get your result

var x = "Tom,Scott,Bob".Split(',').Reverse().ToList<string>()

The difference is that Enumerable.Reverse() returns an IEnumerable<T> instead of being void return

Answer 6

If you are trying to

1. Use multiple delimiters
2. Filter any empty strings
3. Trim leading/trailing spaces

following should work:

string str = "Tom Cruise, Scott, ,Bob | at";
IEnumerable<string> names = str
                            .Split(new char[]{',', '|'})
                            .Where(x=>x!=null && x.Trim().Length > 0)
                            .Select(x=>x.Trim());

Output

• Tom
• Cruise
• Scott
• Bob
• at

Now you can obviously reverse the order as others suggested.