I would like to build a program that would go through a selected folder of .aspx source files and edit them based on the rules I defined in the program.

I haven't really found a good way to get the document's data

example of changes made
<HTML> -> <html> i would like it loop through contents of file and change the uppercase tags to lowercase without changing the data inside the tags.

I've looked at just using regex for this but i wanted to know if there where any html controls that would do this kinda thing.

thanks for the help