title: Best way to add a key/value to an existing URL string?
body: <p>I want to generate a link on my page where a key/value pair is added to the URL dynamically so that:</p>
  
  <blockquote>
    <p><code>Default.aspx?key1=value1</code></p>
  </blockquote>
  
  <p>Becomes:</p>
  
  <blockquote>
    <p><code>Default.aspx?key1=value1&amp;key2=value2</code></p>
  </blockquote>
  
  <p>So that the existing query retains any keys in the URL. Also, if there are no keys, then my key would be added, along with the '<code>?</code>' since it would be needed.</p>
  
  <p>I could easily write some logic that does this, but this seems like something that the framework should have a utiltity for. Is there any way to add keys to a query string without writing my own logic for it?</p>