title: String was not recognized as a valid DateTime on DateTime.ParseExact
body: <p>I know there is a lot of asked question here about <code>DateTime</code> but I saw them all already and seems not to find the right solution for my case.</p>
  
  <p>Here is my code:</p>
  
  <pre><code>return DateTime.ParseExact(partialDate + dtfi.DateSeparator + _baseDate.ToString(), "dd/MM/yyyy", new CultureInfo("en-us");
  </code></pre>
  
  <p>This is throwing me an Exception.</p>
  
  <p>Here is the value of the variables:</p>
  
  <pre><code>string partialDate = "1/22";
  string dtfi.DateSeparator = "/";
  int _baseDate = 2004;
  </code></pre>