var result = obj.createResult(resultType, new List<LineItem>
{
   new LineItem("A"),
   new LineItem("B"))
}.Union(CThoughE(dependency,
   "C",
   "D",
   "E")
).Union(new List<ListItem>
{
   new LineItem("F")
};

return result;


// CThoughE is a new method I created that returns IEnumerable (the utility function returned void)
// createResult(ResultType, IEnumerable<LineItem>)