public bool IsValid()
{
for (int i = 1; i < chain.Count; i++)
{
Block currentBlock = chain[i];
Block previousBlock = chain[i - 1];
if (currentBlock.GetHash() != currentBlock.CalculateHash())
{
return(false);
}
else if (currentBlock.GetPreviousHash() != previousBlock.GetHash())
{
return(false);
}
}
return(true);
}
