title: Add numbers in c#
body: <p>i have a numerical textbox which I need to add it's value to another number 
  I have tried this code</p>
  
  <pre><code>String add = (mytextbox.Text + 2)
  </code></pre>
  
  <p>but it add the number two as another character like if the value of my text box is 13 the result will become 132 </p>