title: Add hours/minute to a datetime variable in C#
body: <p>I want to add 30 minutes to my date time variable.</p>
  <p>My code:</p>
  <pre><code>string time = ViewState[&quot;CloseTime&quot;].ToString();
  DateTime Closetime = DateTime.ParseExact(time, &quot;HH:mm:ss&quot;, CultureInfo.InvariantCulture);
  </code></pre>
  <p>Here my datetime variable is <em>Closetime</em>. I want to add 30 minute to it. How is it possible?</p>