XML : Split XML\CSV file into multiple files based on column heading using JavaScript/C#

I have requirement for splitting a single XML\CSV file into multiple XML\CSV files based on a specific column heading.

For example, I have a file with columns "A B C D" and I want to split the file into two files. The first contains the data from columns from A and B and second from C and D.

Also I want to achieve this by using a JavaScript\C# code.