获取文件hash值

 public string getFilesMD5Hash(string file)
        {
            //MD5 hash provider for computing the hash of the file
            MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider();

            //open the file
            FileStream stream = new FileStream(file, FileMode.Open, FileAccess.Read, FileShare.Read, 8192);

            //calculate the files hash
            md5.ComputeHash(stream);

            //close our stream
            stream.Close();

            //byte array of files hash
            byte[] hash = md5.Hash;

            //string builder to hold the results
            StringBuilder sb = new StringBuilder();

            //loop through each byte in the byte array
            foreach (byte b in hash)
            {
                //format each byte into the proper value and append
                //current value to return value
                sb.Append(string.Format("{0:X2}", b));
            }

            //return the MD5 hash of the file
            return sb.ToString();
        }