文本框.更改前的文本最后值

我有问题与以下代码:一切正常，我想做的是，

当用户改变文本框时，如果它通过了所有的条件(你可以看到我的代码)它将触发一个更新一行的DB查询。现在为了触发这个查询，我需要这个文本框的旧值，在更改之前，现在我如何在不添加变量来存储每个文本框的旧值的情况下做到这一点，我有几个。

是否存在记住旧值的事件?

谢谢。

    private void txt1stRoom_Validated(object sender, EventArgs e)
    {
        if (txt1stRoom.Text == txt1stRoomHuman.Text || txt1stRoom.Text == txt2ndRoom.Text || txt1stRoom.Text == txt3rdRoom.Text)
            MessageBox.Show("Error - Cannot Use Same Monster");
        else if (txt1stRoom.Text != string.Empty)
        {
            SqlConnection cn = new SqlConnection("Data Source=" + serverTbx.Text + ";Initial Catalog=" + dbNameTbx.Text + ";User ID=" + dbUserTbx.Text + ";Password='" + dbPassTbx.Text + "';");
            m_daoManager.init(cn);
            string mobName = m_daoManager.getMonsterName(txt1stRoom.Text);
            m_daoManager.close(cn);
            if (mobName != string.Empty)
            {
                //
                var result1 = MessageBox.Show("Are You Sure u want to change " +lblOrc.Text + "to "+ mobName+ " , Please Notice - This will apply the changes to your database aswell!","Are You Sure?, Please Confirm this Change!", MessageBoxButtons.YesNo);
                if (result1 == System.Windows.Forms.DialogResult.Yes)
                {
                    m_daoManager.init(cn);
                    foreach (int zoneID in Maps.Keys)
                    {
m_daoManager.updateMonstersByZone(BeforeChangetxt1stRoom.Text, AfterChangetxt1stRoom.text, zoneID);
                    }
                    m_daoManager.close(cn);
                    lblOrc.Text = mobName;
                    lblOrc.ForeColor = Color.Green;
                    Properties.Settings.Default.lblOrc1 = lblOrc.Text;
                    Properties.Settings.Default.lblOrc1Color = lblOrc.ForeColor;
                }
            }
            else
            {
                MessageBox.Show("No Monster Found Under this ID");
                txt1stRoom.Text = string.Empty;
                lblOrc.Text = "Enter Mob ID";
                lblOrc.ForeColor = Color.Red;
                Properties.Settings.Default.lblOrc1 = lblOrc.Text;
                Properties.Settings.Default.lblOrc1Color = lblOrc.ForeColor;
            }
            Properties.Settings.Default.Save();
        }
    }