/// <summary>

         /// MD5验证函数

         /// </summary>

         /// <param name="fileName">文件的路径</param>

         /// <param name="blockletter">返回的MD5值是否为大写</param>

         /// <returns></returns>

         public static string GetMD5HashFromFile(string fileName,bool blockletter)

         {

             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++)

                 {

                     if (blockletter)

                         sb.Append(retVal[i].ToString("X2"));

                     else

                         sb.Append(retVal[i].ToString("x2"));

                 }

                 return sb.ToString();

             }

             catch (Exception ex)

             {

                 return "文件读取错误";

             }

         }

         /// <summary>

         ///   计算SHA1值

         /// </summary>

         /// <param name="fileName">文件地址</param>

         /// <param name="blockletter">是否输出大写</param>

         /// <returns></returns>

         public static string GetSHA1HashFromFile(string fileName, bool blockletter)

         {

             var tragetFile = new System.IO.FileStream(fileName, System.IO.FileMode.Open);

             var sha1 = new System.Security.Cryptography.SHA1CryptoServiceProvider();

             byte[] hashbytes = sha1.ComputeHash(tragetFile);

             tragetFile.Close();

             System.Text.StringBuilder sb = new System.Text.StringBuilder();

             for (int i = ; i < hashbytes.Length; i++)

             {

                 if (blockletter) //判断输出大小写

                     sb.Append(hashbytes[i].ToString("X2"));

                 else

                     sb.Append(hashbytes[i].ToString("x2"));

             }

             return sb.ToString();

         }