title: Action immediately after selecting Item
body: <p>I have this code:</p>
  
  <pre><code>    private void button1_Click(object sender, EventArgs e)
      {
  
          if (comboBox1.SelectedItem.ToString() == "blahblah")
          {
              processing ps = new processing();
              pictureBox1.Image = ps.blahblah(bmp);
          }
          else
          {...
          }
      }
  </code></pre>
  
  <p>So the action of the ComboBox is done by clicking on the button1.
  It is possible to take action immediately after selecting Item? without button clicking?</p>