Recursively delete files from a Directory but keeping the dir structure intact

For cleaning up the test files, am trying to do the below. But its not clearing the files as well as not generating an error.

Am I missing something obvious?

    private void CleanUpTempDirFiles()
    {
        var fileGenerationDir = new DirectoryInfo(Path.Combine(Path.GetTempPath(), "TestFilesDir"));

        fileGenerationDir.GetDirectories().ToList().ForEach(dir => dir.GetFiles().ToList().ForEach(file => file.Delete()));
    }