C#

<?xml version="1.0" encoding="utf-8" ?>
<Department name="Computer Science" version="1.0">
  <rules name="Lab1">
    <rule percentage="100" name="Staff" option="default"/>
  </rules>
  <rules name="Lab2">
    <rule percentage="75" name="Hardware" option="default"/>
    <rule percentage="25" name="Software" option="needApproval"/>
  </rules>
</Department>

namespace testrich
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            richTextBox1.AppendText("Original text");
        }

        public void button1_Click(object sender, EventArgs e)
        {
            Form Form2 = new Form2();
            Form2.Show();
        }

        private void button2_Click(object sender, EventArgs e)
        {
            this.Refresh();
        }
    }
}

namespace testrich
{
    public partial class Form2 : Form
    {
        public Form2()
        {
            InitializeComponent();
        }

        public void button1_Click(object sender, EventArgs e)
        {
            Form1 Form1 = new Form1();
            Form1.richTextBox1.AppendText("-Attachment-");
        }
    }
}