hey, I'm stuck again

I have been given a textfile that contains names, departments, email addresses and phone numbers in the format...

firstname, lastname, department, email, phone
firstname2, lastname2, department2, email2, phone2

etc etc...

each persons details are on a different line of the file.

I need to read this data into a vb.net program then do different stuff with it (such as display names of all users in a certain department in a listview etc)

My question is, what is the best way of storing this data in the program? I can't just set up arrays (if that would make sence anyway) for each person as I have no way of knowing how many users details will be supplied in the textfile, but it is likely to be in the hundreds but rising to the thousands later on. I can't just check the textfile each time i need the information as I will need to change data without it changing the textfile.

I'm not looking for the code to do this, just a point in the direction of a method of doing it.

Many thanks for your help.