Recursive functions, directory traversal.

Question

Hi,

Is there a way to recursively iterate a collection, gathering up items into another collection?  As a simple example, consider a inline function that is given a directory and that gathers up all of the files in that directory and all subdirectories, into a single collection.  It's pretty easy to make a recursive function to do this, but I was wondering if it could be done with linq style functors, or similar syntactic goodness.

Thanks.

Answer 1

You could write a simple extension method to perform recursive tasks:

public static class ObjectExtensions
{
    public static IEnumerable<T> Recurse<T>(this T value, Func<T, IEnumerable<T>> recursed)
    {
        yield return value;

        foreach (T rItem in recursed(value))
        {
            foreach (var innerItem in rItem.Recurse(recursed))
                yield return innerItem;

        }
    }
}

Try this usage of the above method:

foreach (var item in @"C:\program files\".Recurse(d => Directory.GetDirectories(d)))
    Console.WriteLine(item);

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Answer 2

Nice.  I like it.  Thanks.