title: Check if non-valued query string exists in url with C#
body: <p>I've seen a couple examples of how to check if a query string exists in a url with C#:</p>
  
  <p><code>www.site.com/index?query=yes</code></p>
  
  <pre><code>if(Request.QueryString["query"]=="yes")
  </code></pre>
  
  <p>But how would I check a string without a parameter? I just need to see if it exists.</p>
  
  <p><code>www.site.com/index?query</code></p>
  
  <pre><code>if(Request.QueryString["query"] != null) //why is this always null?
  </code></pre>
  
  <p>I know there's probably a simple answer and I'll feel dumb, but I haven't been able to find it yet. Thanks!</p>