1.方法1

private 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 = 0; i < retVal.Length; i++)
 {
 sb.Append(retVal[i].ToString(“x2″));
 }
 return sb.ToString();
 }
 catch (Exception ex)
 {
 throw new Exception(“GetMD5HashFromFile() fail,error:” + ex.Message);
 }
 }
2.方法2

    //计算文件的MD5码

        private string getMD5Hash(string pathName)

        {

            string strResult = "";

            string strHashData =http://www.mamicode.com/ "";

            byte[] arrbytHashValue;

            System.IO.FileStream oFileStream = null;

            System.Security.Cryptography.MD5CryptoServiceProvider oMD5Hasher = new System.Security.Cryptography.MD5CryptoServiceProvider();

　　　　try

            {

                oFileStream = new System.IO.FileStream(pathName, System.IO.FileMode.Open, System.IO.FileAccess.Read, System.IO.FileShare.ReadWrite));

                arrbytHashValue = http://www.mamicode.com/oMD5Hasher.ComputeHash(oFileStream);//计算指定Stream 对象的哈希值

                oFileStream.Close();

                //由以连字符分隔的十六进制对构成的String，其中每一对表示value 中对应的元素；例如“F-2C-4A”

                strHashData = http://www.mamicode.com/System.BitConverter.ToString(arrbytHashValue);

                //替换-

                strHashData = http://www.mamicode.com/strHashData.Replace("-", "");

                strResult = strHashData;

            }

            catch (System.Exception ex)

            {

                MessageBox.Show(ex.Message);

　　　　　}

            return strResult;

        }

3.比较。

方法1和方法2虽然都能计算文件的MD5，但是方法2在针对大文件时，更快，所以更好。

C# MD5校验