Thu, 11. Mar 2010
Lazy Sequence of Directory Descendants in C#

Chris Sells translated a Clojure implementation of a function that descends into a directory in a "lazy" manner by Craig Andera into C# but his solution is so .NET 2.0 ;-).

Here's my take

    static IEnumerable<string> GetDirectoryDescendants(string path) {
        return Directory.GetFiles(path)
            .Concat(Directory.GetDirectories(path)
                .SelectMany<string, string>(GetDirectoryDescendants)
            );
    }

where I'd hope C# 4.0's compiler will be able to deduce the types for the SelectMany itself. Interestingly the C# 3.0 compiler does fine when I use a lambda expression instead: 

    static IEnumerable<string> GetDirectoryDescendants(string path) {
        return Directory.GetFiles(path)
            .Concat(Directory.GetDirectories(path)
                .SelectMany(dir => GetDirectoryDescendants(dir))
            );
    }

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