Fill empty excel cells with the under value c#?

Question

When I upload Excel file, I am wonder how to fill empty cell in row with next value in C#? For example:

from this  => to be like this
11                       11
                         30
30                       30
34                       34
                         55  
55                       55

What you tried so far? Show us some code? Any error then it should be part of your question. Please read minimal reproducible example — Prasad Telkikar
@PrasadTelkikar Mostly I asked to someone give some kind of idea, not code.... Cause I am not sure about algorithm — Stephen K
Hi Stephen, We are here to help you, but we would like to see some efforts from OP. Someone randomly post a question and seek for help that will not much helpful for OP as well as person who is going to refer this question in future. So Kindly show us your efforts. I would highly recommend you to read How to ask a good question — Prasad Telkikar