Question

Let’s assume that I have a collection of strings, like so:

IList<string> myList = new List<string>(){"one", "two", "three"};

Using myList.Aggregate I would like to end up with “‘one’, ‘two’, ‘three'” (including single quotes)

Does someone have a sleak way of doing this, only using the Aggregate function? I was thinking something in the lines of

myList.Aggregate((increment, seed) => string.Concat(increment, ", ", seed));

but that’s only half the solution.

Answer 1

Any reason to use Aggregate rather than the simpler string.Join?

string joined = string.Join(", ", myCollection.Select(x => "'" + x + "'"));

(Add a ToArray call if you’re using .NET 3.5.)

You can implement string.Join using Aggregate (ideally using a StringBuilder) but it’s not terribly pleasant. Assuming a non-empty collection, I think this should do it:

string csv = myCollection.Aggregate(new StringBuilder("'"),
                 (sb, x) => sb.AppendFormat("{0}', '"),
                 sb => { sb.Length -= 3;
                         return sb.ToString(); });