Csv file import

Question

Hi, 
I have a general question on CSV import and I am sorry if this has been asked before on this forum. 
So, I have a UI page with the data entry fields. I have to implement import functionality by which user can select the csv file and when they load it, the appropriate data entry field should populate the value. 

What is the best way ( performance wise) to accomplish this?

Any suggestion is highly appreciated.