C# 获取一个文件的MD5值

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace ConsoleApplication6
{
    public class Program
    {
        public static void Main(string[] args)
        {
            string fileName = @"D:\说明.txt";
            string result = GetMD5HashFromFile(fileName);
        }

        // <summary>
        /// 计算文件的MD5校验
        /// </summary>
        /// <param name="fileName"></param>
        /// <returns></returns>
        public static string GetMD5HashFromFile(string fileName)
        {
            try
            {
                FileStream file = new FileStream(fileName, FileMode.Open);
                System.Security.Cryptography.MD5 md5 = new System.Security.Cryptography.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);
            }
        }
    }
}