title: c# - datatable if one field is null set another value
body: <p>I have a Datatable.</p>
  
  <pre><code>using (DataSet ds = new DataSet())
  {
      da.Fill(ds);
      dt = ds.Tables[0];
  }
  </code></pre>
  
  <p>The <code>dt</code>, return list of data like this,</p>
  
  <p><a href="https://i.stack.imgur.com/2mjwr.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/2mjwr.png" alt="enter image description here"></a></p>
  
  <p>From this image, when UserId is DBnull then I want to set docCount equl to 0. How can I do that?</p>