title: How to insert null value in Database through parameterized query
body: <p>I have a <code>datetime</code> datatype : <code>dttm</code></p>
  
  <p>Also the database field type is <code>datatime</code></p>
  
  <p>Now I am doing this:</p>
  
  <pre><code>if (dttm.HasValue)
  {
      cmd.Parameters.AddWithValue("@dtb", dttm);
  }
  else
  {
      // It should insert null value into database
      // through cmd.Parameters.AddWithValue("@dtb", _____)
  }
  </code></pre>
  
  <p>How can this be done.</p>