c#md5与SHA1验证函数

 /// <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();
         }