title: how to remove duplicate values from a list but want to include all empty strings from that list
body: <p>I have a list of objects in which I want to remove duplicates but does not want to remove blank objects. 
  I am using DistinctBy lambda expression. But it also removes duplicates.
  Can anyone help me in providing the condition that passes blank and checks only that object which has proper value in an object ?</p>