first windows application - web browser

I have a 2 part browser you can either select from a list of URLs and surf or type your own url in (this part doesn't work)

here are my bits of code

private void button1_Click(object sender, EventArgs e)

webBrowser1.Navigate(new Uri(comboBox1.SelectedItem.ToString()));

label1.Text = "now you're surfing the net!";

private void button2_Click(object sender, EventArgs e)