c# 如何給文件計算MD5

在項目中，當我們需要把數據文件上傳到ftp時，為了保證數據的完整性，我們會計算數據文件的MD5，并把MD5文件和數據文件一同上傳。

那么如何產生數據文件的MD5呢？

我們可以通過System.Security.Cryptography.MD5類來

private void WriteMD5(string zipFile, string ctrlFile)
        {
            // Add hash code to ctrl file
            byte[] validHash = GenerateMD5Hash(zipFile);
            // make sure that we add hash value in a new line
            bool addNewLine = false;
            using (StreamReader sr = new StreamReader(ctrlFile))
            {
                string[] lines = sr.ReadToEnd().Split(new char[] { '\n' });
                if (lines.Length == 1) addNewLine = true;
            }

            // ready to put the control file, so add the hash string to it
            using (StreamWriter sw = new StreamWriter(ctrlFile, true))
            {
                if (addNewLine) sw.WriteLine("");
                sw.WriteLine(BitConverter.ToString(validHash).Replace("-", ""));
            }
        }

private byte[] GenerateMD5Hash(string localFileName)
        {
            byte[] localHash = null;
            using (MD5 md5Hash = MD5.Create())
            {
                using (FileStream localFile = File.OpenRead(localFileName))
                {
                    localHash = md5Hash.ComputeHash(localFile);
                }
            }
            return localHash;
        }