title: passing a null datetime to reportparameter class?
body: <p>How can I put a null value on datetime variable type?</p>
  
  <p>I tried to make it nullable value, but I need to use it in <code>ReportParameter()</code> method to send it to my report but <code>ReportParameter()</code> constructor cannot take a nullable value and the ReportParameter() take just a string values!</p>