private static IEnumerable<string> Traverse(string rootDirectory)

{

    IEnumerable<string> files = Enumerable.Empty<string>();

    IEnumerable<string> directories = Enumerable.Empty<string>();

    try

    {

        // The test for UnauthorizedAccessException.

        var permission = new FileIOPermission(FileIOPermissionAccess.PathDiscovery, rootDirectory);

        permission.Demand();

​

        files = Directory.GetFiles(rootDirectory);

        directories = Directory.GetDirectories(rootDirectory);

    }

    catch

    {

        // Ignore folder (access denied).

        rootDirectory = null;

    }

​

    if (rootDirectory != null)

        yield return rootDirectory;

​

    foreach (var file in files)

    {

        yield return file;

    }

​

    // Recursive call for SelectMany.

    var subdirectoryItems = directories.SelectMany(Traverse);

    foreach (var result in subdirectoryItems)

    {

        yield return result;

    }

}

string[] files = Directory.GetFiles(@"C:\\", "*.*", SearchOption.AllDirectories);