title: How to set default value
body: <p>I am trying to parse a csv file using csv helper</p>
  
  <p>this is my maping class</p>
  
  <pre><code>sealed class CSVFileDefinitionMapFinal : CsvClassMap&lt;CSVFileDefinitionFinal&gt;
  { 
      public CSVFileDefinitionMapFinal()
      {
          Map(m =&gt; m.FARM_ID).Name("FRM_ID");
      }
  }
  </code></pre>
  
  <p>this is my item class</p>
  
  <pre><code>class CSVFileDefinitionFinal
  {
      public int FARM_ID { get; set; }
  }
  </code></pre>
  
  <p>the problem is that the <code>FRM_ID</code> in the csv may hav <code>null</code>. so when I do the mappign above, I have an exception that null can't be transfer to integer. I am asking about if there is a way to try and catch that and set the value to -10 when it is null.</p>
  
  <p>the try and catch should be in the maping class, but I couldn't know what to do after catching the exception. in other words, i couldn't know how to set <strong>default value</strong> to the maping object</p>