In visual studio 2008 they moved all the objects and functions dealing with files into a namespace called "System.IO" this namespace provides objects for things like files, directories and file streams... which you would use to open, write and close files.
One object you will want to lookup is called "StreamReader". This object allows you to open a file and returns a stream. This stream object has methods like read and readLine. As you can imagine if there is a reader there is a writer. The object "StreamWriter" can be used for writing to files. Again it opens up files and creates a stream that you can use to get access to methods like write and writeLine.
Lookup these two objects and look for examples on both the DIC board and on the web and you will see plenty of code to show you how they are used.
If you have any more questions about them, you can ask us and I am sure we will be glad to help.
Enjoy!