title: How to check for null values in a SqlDataReader without using more than one reader
body: <p>I have a table that has a few columns that sometimes will have a null value. How can I check if a value is null, and if so set the value to an empty string or something that I can use later?</p>
  
  <pre><code>private DateTime dtDate_Ordered;
  private DateTime dtDate_Required;
  private DateTime dtDate_Received;
  
  var stringSql = "select * from po where po_num=" + stringPO_NUM;
  
  var Class_Connection = new SQL_Connection();
  
  Class_Connection.cnn.Close();
  Class_Connection.cnn.Open();
  
  try
  {
      var cmd = new SqlCommand(stringSql, Class_Connection.cnn);
      SqlDataReader sdr = cmd.ExecuteReader();
  
      while (sdr.Read())
      {
          dtDate_Ordered = (DateTime)sdr["dateordered"];
          dtDate_Required = (DateTime)sdr["daterequired"];
          dtDate_Received = (DateTime)sdr["daterecv"];
          stringComments = (string)sdr["comments"];
      }
  }
  catch (Exception Ex)
  {
      Class_Connection.cnn.Close();
      throw Ex;
  }
  
  Class_Connection.cnn.Close();
  
  RDI_Date_Ordered.SelectedDate = dtDate_Ordered;
  RDI_Date_Required.SelectedDate = dtDate_Required;
  RDI_Date_Received.SelectedDate = dtDate_Received;
  </code></pre>
  
  <p>I would like to be able to handle the null value, before the exception handler catches it.</p>