Create random file

random.cs

        private static void CreateRandomTempFile(string fileName, long lengthInMb)
        {
            // https://stackoverflow.com/questions/4432178/creating-a-random-file-in-c-sharp
            byte[] data = new byte[lengthInMb * 1024 * 1024];
            Random rng = new Random();
            rng.NextBytes(data);
            File.WriteAllBytes(fileName, data);
        }