title: Use .DefaultIfEmpty() instead of .FirstOrDefault() ?? String.Empty;
body: <p>How can I integrate the <code>.DefaultIfEmpty()</code> extension method so I have <strong>not</strong> to use </p>
  
  <pre><code>.FirstOrDefault() ?? String.Empty;
  </code></pre>
  
  <p>Code:</p>
  
  <pre><code>(from role in roleList
  let roleArray = role.RoleId.Split(new char[] { WorkflowConstants.WorkflowRoleDelimiter })
  where roleArray.Length.Equals(_SplittedRoleIdArrayLength) &amp;&amp; 
        HasAccessToCurrentUnit(roleArray[_UnitIndexInRoleId])
  select roleArray[_LevelIndexInRoleId]).FirstOrDefault() ?? String.Empty;
  </code></pre>