BLL.Image.Calculate_Hash C# (CSharp) Метод

        public static string Calculate_Hash(string fileName)
        {
            long read = 0;
            var r = -1;
            const long bytesToRead = 100 * 1024 * 1024;
            const int bufferSize = 4096;
            var buffer = new byte[bufferSize];
            var sha = new SHA256Managed();

            using (var stream = new FileStream(fileName, FileMode.Open, FileAccess.Read))
            {
                while (read <= bytesToRead && r != 0)
                {
                    read += (r = stream.Read(buffer, 0, bufferSize));
                    sha.TransformBlock(buffer, 0, r, null, 0);
                }
            }
            sha.TransformFinalBlock(buffer, 0, 0);
            return string.Join("", sha.Hash.Select(x => x.ToString("x2")));
        }