获取文件的MD5码（C#）

using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;

namespace Test
{
    public class MD5Code
    {
        /// <summary>
        /// 获取文件的MD5码
        /// </summary>
        /// <param name="fileName">传入的文件名（含路径及后缀名）</param>
        /// <returns></returns>
        public string GetMD5HashFromFile(string fileName)
        {
            try
            {
                FileStream file = new FileStream(fileName, System.IO.FileMode.Open);
                MD5 md5 = new MD5CryptoServiceProvider();
                byte[] retVal = md5.ComputeHash(file);
                file.Close();
                StringBuilder sb = new StringBuilder();
                for (int i = ; i < retVal.Length; i++)
                {
                    sb.Append(retVal[i].ToString("x2"));
                }
                return sb.ToString();
            }
            catch (Exception ex)
            {
                throw new Exception("GetMD5HashFromFile() fail,error:" + ex.Message);
            }
        }
    }
}