public struct Block 
{ 
  /// <summary> 
  /// 區(qū)塊位置 
  /// </summary> 
  public int Index { get; set; } 
  /// <summary> 
  /// 區(qū)塊生成時間戳 
  /// </summary> 
  public string TimeStamp { get; set; } 
  /// <summary> 
  /// 心率數(shù)值 
  /// </summary> 
  public int BPM { get; set; } 
  /// <summary> 
  /// 區(qū)塊 SHA-256 散列值 
  /// </summary> 
  public string Hash { get; set; } 
  /// <summary> 
  /// 前一個區(qū)塊 SHA-256 散列值 
  /// </summary> 
  public string PrevHash { get; set; } 
  /// <summary> 
  /// 下一個區(qū)塊生成難度 
  /// </summary> 
  public int Difficulty { get; set; } 
  /// <summary> 
  /// 隨機值 
  /// </summary> 
  public string Nonce { get; set; } 
}

/// <summary> 
/// 校驗 Hash 是否有效 
/// </summary> 
/// <param name="hashStr">Hash 值</param> 
/// <param name="difficulty">難度</param> 
/// <returns></returns> 
public static bool IsHashValid(string hashStr, int difficulty) 
{ 
      var bytes = Enumerable.Range(0, hashStr.Length) 
        .Where(n => n % 2 == 0) 
        .Select(n => Convert.ToByte(hashStr.Substring(n, 2), 16)) 
        .ToArray(); 
      var bits = new BitArray(bytes); 
      for (var i = 0; i < difficulty; i++) 
      { 
        if (bits[i]) return false; 
      } 
      return true; 
}

/// <summary> 
/// 計算區(qū)塊 HASH 值 
/// </summary> 
/// <param name="block">區(qū)塊實例</param> 
/// <returns>計算完成的區(qū)塊散列值</returns> 
public static string CalculateHash(Block block) 
{ 
  string calculationStr = $"{block.Index}{block.TimeStamp}{block.BPM}{block.PrevHash}{block.Nonce}"; 
  SHA256 sha256Generator = SHA256.Create(); 
  byte[] sha256HashBytes = sha256Generator.ComputeHash(Encoding.UTF8.GetBytes(calculationStr)); 
  StringBuilder sha256StrBuilder = new StringBuilder(); 
  foreach (byte @byte in sha256HashBytes) 
  { 
    sha256StrBuilder.Append(@byte.ToString("x2")); 
  } 
  return sha256StrBuilder.ToString(); 
}

/// <summary> 
/// 生成新的區(qū)塊 
/// </summary> 
/// <param name="oldBlock">舊的區(qū)塊數(shù)據(jù)</param> 
/// <param name="BPM">心率</param> 
/// <returns>新的區(qū)塊</returns> 
public static Block GenerateBlock(Block oldBlock, int BPM) 
{ 
  Block newnewBlock = new Block() 
  { 
    Index = oldBlock.Index + 1, 
    TimeStamp = CalculateCurrentTimeUTC(), 
    BPMBPM = BPM, 
    PrevHash = oldBlock.Hash, 
    DifficultyDifficulty = Difficulty 
  }; 
  // 挖礦 ing... 
  for (int i = 0; ; i++) 
  { 
    newBlock.Nonce = i.ToString("x2"); 
    if (!IsHashValid(CalculateHash(newBlock), Difficulty)) 
    { 
      Console.WriteLine($"目前結(jié)果：{CalculateHash(newBlock)} ，正在計算中..."); 
      Task.Delay(1); 
      continue; 
    } 
    else 
    { 
      Console.WriteLine($"目前結(jié)果：{CalculateHash(newBlock)} ，計算完畢..."); 
      newBlock.Hash = CalculateHash(newBlock); 
      break; 
    } 
  } 
  // 原有代碼 
  // newBlock.Hash = CalculateHash(newBlock); 
  return newBlock; 
}