Counting file bytes example

CountFileBytes.cs

public static long CountFileBytes(string directory, bool recursive)
{
    return (new FileSystemEnumerable<long>(
        directory,
        (ref FileSystemEntry entry) => entry.Length,
        new EnumerationOptions() { RecurseSubdirectories = recursive })
    {
        ShouldIncludePredicate = (ref FileSystemEntry entry) => !entry.IsDirectory
    }).Sum();
}