Functional programming with Linq – IEnumerable.Aggregate

As I was learning functional programming with F# I came across the List.reduce function which iterates through a list and builds up an accumulator value by running another function against each element in the list.

Back to the more familiar C# territory, LINQ has introduced some functional features to C# and one of these is the Aggregate function on IEnumerable<T> which works in the same way as the List.reduce function.

In the following example, you can use the Aggregate function to built up a comma separated string from an array of string:

var strings = new List<string> { "Jack", "Jill", "Jim", "Joe", "Jane" };
// this returns "Jack, Jill, Jim, Joe, Jane"
var comSeparatedStrings = strings.Aggregate((acc, item) => acc + ", " + item);