Sorting a CSV

Hello, 

I'm running into some difficulties on a small application I'm writing. I have a scenario where I have a master database file (.csv) and 50+ store database files (.csv). I need to check that the entries inside of the master database file exist in the individual store database files. Originally I had written this with formulas for Excel but it was taking too much time per data set to be viable. I figured out the logic of checking line by line against the store file using a while loop, but I ran into the problem of non alpha numeric sorting. Without a line of code to set my stream reader at index of 0 at each run it wouldn't scan the whole document. This wasn't viable because each document is 25,000+ items causing the code to run through 2.8 million times on average per validation check. My code works if the data is in a sorted format, but I wanted the application to have the tools to sort the data itself. 

So. .. .  long story short, I need help writing the code for taking an item selected by an open file dialog, parsing through its contents and sorting it into least to greatest fashion. I need to make sure that the data when sorted maintains integrity (i.e. if the first line contains 1,2,3,4 I only need it sorted off of the first entry (1) but for it to keep all of its trailing data. 

 Any help is appreciated. 

Thanks, 

Cuken