title: How to check if an appSettings key exists?
body: <p>How do I check to see if an Application Setting is available?  </p>
  
  <p>i.e. app.config</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8" ?&gt;
  &lt;configuration&gt;
    &lt;appSettings&gt;
      &lt;add key ="someKey" value="someValue"/&gt;
    &lt;/appSettings&gt;
  &lt;/configuration&gt;
  </code></pre>
  
  <p>and in the codefile</p>
  
  <pre><code>if (ConfigurationManager.AppSettings.ContainsKey("someKey"))
  {
    // Do Something
  }else{
    // Do Something Else
  }
  </code></pre>