How to calculate checksum using fileStream object in dotnet

Calculate checksum using fileStream object in dotnet

using System;

using System.Reflection;

using System.Security.Cryptography;

using System.Text;

using System.IO;

using System.IO.Abstractions;

namespace Helper.Utility

{

//Class CrcUtil.cs used get filestream using filepath for calculating checksum

    public class CrcUtil

    {

        private readonly IFileSystem _fileSystem;

        public CrcUtil(IFileSystem fileSystem)

        {

            _fileSystem = fileSystem;

        }

        public string GetCrcCode(string filePath)

        {

            try

            {

                using (var stream = _fileSystem.File.Open(filePath, FileMode.Open, FileAccess.Read, FileShare.Read))

                {

                    return GetCrcCode(stream);

                }

            }

            catch (Exception ex)

            {

                // SsiLogger.Logger.Error("Exception occured in CrcUtil {0} for file {1}", ex.Message, filePath);

                // SsiLogger.Logger.Debug(ex);

                throw;

            }

        }

        public string GetCrcCode(Stream fileStream)

        {

            try

            {

                return Md5HashGenerator.GenerateKey(fileStream);

            }

            catch (Exception ex)

            {

                // SsiLogger.Logger.Error("Exception occured in CrcUtil {0}", ex.Message);

                // SsiLogger.Logger.Debug(ex);

                throw;

            }

        }

    }

//Class Md5HashGenerator.cs used for calculating checksum of passed filestream

    public class Md5HashGenerator

    {

        public static String GenerateKey(Stream sourceObject)

        {

            //Catch unuseful parameter values

            if (sourceObject == null)

            {

                throw new ArgumentNullException("sourceObject");

            }

            //We determine if the passed object is really serializable.

            try

            {

                //Now we begin to do the real work.

                var hashString = ComputeHash(sourceObject);

                return hashString;

            }

            catch (AmbiguousMatchException ame)

            {

                throw new ApplicationException(string.Format("Could not definitly decide if object is serializable. Message:{0}", ame.Message));

            }

            catch (Exception ex)

            {

                // SsiLogger.Logger.Error("Exception occured in Md5HashGenerator {0}", ex.Message);

                // SsiLogger.Logger.Debug(ex);

                throw;

            }

        }

        private static string ComputeHash(Stream objectAsBytes)

        {

            MD5 md5 = new MD5CryptoServiceProvider();

            try

            {

                var result = md5.ComputeHash(objectAsBytes);

                // Build the final string by converting each byte

                // into hex and appending it to a StringBuilder

                var stringBuilder = new StringBuilder();

                foreach (var data in result)

                {

                    stringBuilder.Append(data.ToString("X2"));

                }

                // And return it

                return stringBuilder.ToString();

            }

            catch (ArgumentNullException)

            {

                //If something occured during serialization, this method is called with an null argument.

                // SsiLogger.Logger.Error("Hash has not been generated.");

                return null;

            }

            catch (Exception ex)

            {

                // SsiLogger.Logger.Error("Exception occured in Md5HashGenerator {0}", ex.Message);

                // SsiLogger.Logger.Debug(ex);

                throw;

            }

        }

    }

}