private void add_Click(object sender, EventArgs e)
{
ReceiptAdd receiptAdd = new ReceiptAdd();
reset();
receiptAdd.Show();
this.Visible = false;
}
private void btnPayment_Click(object sender, EventArgs e)
{
ReceiptAdd receipt = new ReceiptAdd(txtContractId.Text, txtCustomerName.Text, "", txtRest.Text, "Kí hợp đồng thuê nhà");
receipt.Show();
}