c#中对事务的处理(部分)

private bool TransferAccount()
{
bool flag = false;
string transferFrom=cbbTransferFrom.SelectedValue.ToString();
string transferTo=cbbTransferTo.SelectedValue.ToString();
if (tbAccounts.Text=="")
{
MessageBox.Show("请输入转账金额");
tbAccounts.Focus();
}
else
{
int account = int.Parse(tbAccounts.Text.ToString());
if (transferFrom != transferTo)
{
cn = GetCn();
SqlTransaction st = cn.BeginTransaction();
cmd = cn.CreateCommand();
cmd.Transaction = st;
try
{
cmd.CommandText = string.Format("update bankAccount set bankroll=bankroll+{0} where id={1}", -account, transferFrom);
cmd.ExecuteNonQuery();
cmd.CommandText = string.Format("update bankAccount set bankroll=bankroll+{0} where id={1}", account, transferTo);
cmd.ExecuteNonQuery();
st.Commit();
flag = true;
}
catch
{
st.Rollback();
}
}
else
{
MessageBox.Show("不能给自己转账");
}
}
return flag;