C#如何让winform程序中的输入文本框保留上次的输入

private Settings settings = new Settings();

        private void MainForm_Load(object sender, EventArgs e)
        {
            this.txtTargetInitialCatalog.Text = settings.sadbname;
        }

        private void MainForm_FormClosing(object sender, FormClosingEventArgs e)
        {
            settings.sadbname = this.txtTargetInitialCatalog.Text;
            settings.Save();
        }

private void textBox1_KeyUp(object sender, KeyEventArgs e)
        {
            if (e.KeyCode == Keys.Control || e.KeyCode == Keys.Enter)
            {
                button1.Focus();
                button1_Click(sender, e);
            }
        }