C# Code to Change a Selected Richtext Box Text to Upper Case

private void button1_Click(object sender, EventArgs e)
{
    System.Drawing.Font font =
        new System.Drawing.Font(richTextBox1.SelectionFont.FontFamily, richTextBox1.SelectionFont.Size,
            richTextBox1.SelectionFont.Style);
    string strText = richTextBox1.SelectedText;
    richTextBox1.SelectedText = strText.ToUpper();
    richTextBox1.SelectionFont = font;
}