private void newBlock_Click(object sender, EventArgs e)
{
// transactions to be included within the new block.
List <Transaction> transactions = blockchain.getPendingTransactions();
// Create the new block w/ the transactions from the pool
Block newBlock = new Block(blockchain.getPrevBlock(), transactions, publicKey.Text);
// the block w/ transactions is added to the blockchain
blockchain.Blocks.Add(newBlock);
// the blockchain is printed to the UI.
richTextBox1.Text = blockchain.ToString();
}