public struct Block
{
/// <summary>
/// 区块位置
/// </summary>
public int Index { get; set; }
/// <summary>
/// 区块生成时间戳
/// </summary>
public string TimeStamp { get; set; }
/// <summary>
/// 心率数值
/// </summary>
public int BPM { get; set; }
/// <summary>
/// 区块 SHA-256 散列值
/// </summary>
public string Hash { get; set; }
/// <summary>
/// 前一个区块 SHA-256 散列值
/// </summary>
public string PrevHash { get; set; }
}

public static class BlockGenerator
{
public static List<Block> _blockChain = new List<Block>();
}


/// <summary>
/// 计算区块 HASH 值
/// </summary>
/// <param name="block">区块实例</param>
/// <returns>计算完成的区块散列值</returns>
public static string CalculateHash(Block block)
{
string calculationStr = $"{block.Index}{block.TimeStamp}{block.BPM}{block.PrevHash}";

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>
/// 生成新的区块
/// </summary>
/// <param name="oldBlock">旧的区块数据</param>
/// <param name="BPM">心率</param>
/// <returns>新的区块</returns>
public static Block GenerateBlock(Block oldBlock, int BPM)
{
Block newBlock = new Block()
{
Index = oldBlock.Index + 1,
TimeStamp = CalculateCurrentTimeUTC(),
BPM = BPM,
PrevHash = oldBlock.Hash
};

newBlock.Hash = CalculateHash(newBlock);
return newBlock;
}

/// <summary>
/// 计算当前时间的 UTC 表示格式
/// </summary>
/// <returns>UTC 时间字符串</returns>
public static string CalculateCurrentTimeUTC()
{
DateTime startTime = new DateTime(1970, 1, 1, 0, 0, 0, 0);
DateTime nowTime = DateTime.Now;

long unixTime = (long)Math.Round((nowTime - startTime).TotalMilliseconds, MidpointRounding.AwayFromZero);
return unixTime.ToString();
}


/// <summary>
/// 检验区块是否有效
/// </summary>
/// <param name="newBlock">新生成的区块数据</param>
/// <param name="oldBlock">旧的区块数据</param>
/// <returns>有效返回 TRUE，无效返回 FALSE</returns>
public static bool IsBlockValid(Block newBlock, Block oldBlock)
{
if (oldBlock.Index + 1 != newBlock.Index) return false;
if (oldBlock.Hash != newBlock.PrevHash) return false;
if (CalculateHash(newBlock) != newBlock.Hash) return false;

return true;
}

/// <summary>
/// 如果新的区块链比当前区块链更新，则切换当前区块链为最新区块链
/// </summary>
/// <param name="newBlockChain">新的区块链</param>
public static void SwitchChain(List<Block> newBlockChain)
{
if (newBlockChain.Count > _blockChain.Count)
{
_blockChain = newBlockChain;
}
}


现在整个区块链的基本操作已经完成，现在我们需要让他运转起来，我们来到 StartUp 当中，添加两个新的路由：
app.Map("/BlockChain", _ =>
{
_.Run(async context =>
{
if (context.Request.Method == "POST")
{
// 增加区块链
if (BlockGenerator._blockChain.Count == 0)
{
Block firstBlock = new Block()
{
Index = 0,
TimeStamp = BlockGenerator.CalculateCurrentTimeUTC(),
BPM = 0,
Hash = string.Empty,
PrevHash = string.Empty
};

BlockGenerator._blockChain.Add(firstBlock);

await context.Response.WriteAsync(JsonConvert.SerializeObject(firstBlock));
}
else
{
int.TryParse(context.Request.Form["BPM"][0], out int bpm);

Block oldBlock = BlockGenerator._blockChain.Last();
Block newBlock = BlockGenerator.GenerateBlock(oldBlock, bpm);

if (BlockGenerator.IsBlockValid(newBlock, oldBlock))
{
List<Block> newBlockChain = new List<Block>();
foreach (var block in BlockGenerator._blockChain)
{
newBlockChain.Add(block);
}

newBlockChain.Add(newBlock);
BlockGenerator.SwitchChain(newBlockChain);
}

await context.Response.WriteAsync(JsonConvert.SerializeObject(newBlock));
}
}
});
});

app.Map("/BlockChains", _ =>
{
_.Run(async context =>
{
await context.Response.WriteAsync(JsonConvert.SerializeObject(BlockGenerator._blockChain));
});
});