private void button1_click(object sender, EventArgs e)
{
    conn.Open();

    if (textBox3.Text.Trim() == textBox4.Text.Trim() && IsValidEmail(textBox1.Text))
    {
        MySqlCommand comm = conn.CreateCommand();
        comm.CommandText = "INSERT into users(userName, password, email) values(@user,@pass,@mail)";
        MySqlTransaction tx = conn.BeginTransaction();
        comm.Transaction = tx;
        try
        {
            comm.Parameters.AddWithValue("@user", MySqlDbType.Text).Value = textBox2.Text;
            comm.Parameters.AddWithValue("@pass", MySqlDbType.Text).Value = textBox3.Text;
            comm.Parameters.AddWithValue("@mail", MySqlDbType.Text).Value = textBox1.Text;
            comm.ExecuteNonQuery();
            tx.Commit();
        }
        catch
        {
            MessageBox.Show("Error!");
        }
        finally
        {
            conn.Close();
        }
    }
}

我不知道我做错了什么。