C # computes the SHA256 value of a file

static void Main (string [] args)
        {
            Console.WriteLine (SHA256File (@ "C: \ BaiduYunDownload \ 66666.jpg"));
        }


        /// Calculate the SHA256 value of the file
        /// </ summary>
        /// <param name = "fileName"> File name and path to calculate SHA256 value </ param>
        /// <returns> SHA256 value hex string </ returns>
        public static string SHA256File (string fileName)
        {
            return HashFile (fileName, "sha256");
        }

        /// <summary>
        /// Calculate the hash value of the file
        /// </ summary>
        /// <param name = "fileName"> File name and path to calculate hash value </ param>
        /// <param name = "algName"> Algorithm: sha1, md5 </ param>
        /// <returns> hash hex string </ returns>
        public static string HashFile (string fileName, string algName)
        {
            if (! System.IO.File.Exists (fileName))
                return string.Empty;

            FileStream fs = new FileStream (fileName, FileMode.Open, FileAccess.Read);
            byte [] hashBytes = HashData (fs, algName);
            fs.Close ();
            return ByteArrayToHexString (hashBytes);
        }


        /// <summary>
        /// convert byte array to hexadecimal string
        /// </ summary>
        public static string ByteArrayToHexString (byte [] buf)
        {
            string returnStr = "";
            if (buf! = null)
            {
                for (int i = 0; i <buf.Length; i ++)
                {
                    returnStr + = buf [i] .ToString ("X2");
                }
            }
            return returnStr;
        }


        /// <summary>
        /// Calculate the hash value
        /// </ summary>
        /// <param name = "stream"> Stream to be hashed </ param>
        /// <param name = "algName"> Algorithm: sha1, md5 </ param>
        /// <returns> Hash byte array </ returns>
        public static byte [] HashData (Stream stream, string algName)
        {
            HashAlgorithm algorithm;
            if (algName == null)
            {
                throw new ArgumentNullException ("algName cannot be null");
            }
            if (string.Compare (algName, "sha256", true) == 0)
            {
                algorithm = SHA256.Create ();
            }
            else
            {
                if (string.Compare (algName, "md5", true)! = 0)
                {
                    throw new Exception ("algName can only use sha256 or md5");
                }
                algorithm = MD5.Create ();
            }
            return algorithm.ComputeHash (stream);
        } 

C # computes the SHA256 value of a file