VS 2010 Working with text files to read/write configurations

I'm writting a program where I save the properties of the program in a text file.
In the 4 combo-boxes I select the properties and I want the program to save the index of the combobox in the txt file.

Example:
In the first combo box I select the 0
In the second... the 4
etc...

In the text file I want to save:
0
4
...
The first line correspond to the first combo box, and so on...

I've to said that the last week I stopped using VB6 and I started with VB.Net 2010, so I've found some differences.