title: implicit conversion between '<null>' and 'System.DateTime' error
body: <pre><code>private DateTime? pApproveDate=null;
  pApproveDate =(Reader["ApproveDate"]==DBNull.Value)?null: Convert.ToDateTime(Reader["ApproveDate"]);
  </code></pre>
  
  <p>Above code is generating the following error during compile time- 
  <strong>Type of conditional expression cannot be determined because there is no implicit conversion between '' and 'System.DateTime'</strong></p>