title: Operator '??' cannot be applied to operands of type 'System.DateTime'
body: <p>I get the following error :</p>
  
  <pre><code>Operator '??' cannot be applied to operands of type 'System.DateTime'
  </code></pre>
  
  <hr>
  
  <pre><code> foreach (EndServReward r in reward)
                              {
                                  if (con.State == ConnectionState.Closed)
                                  {
                                      con.Open();
                                  }
                                  myIfxCmd.Parameters[0].Value = r.EmpNum ;
                                  myIfxCmd.Parameters[1].Value = (r.ServDate) ?? DBNull.Value;
                              }
  </code></pre>
  
  <hr>
  
  <p>where <code>reward is List&lt;EndServReward&gt; reward</code>,why this happens ,and how to fix it ?</p>