I just want to edit a txt and save the edited version.

In this case i replaced all the i's with q's.

Is there an easier way to do this? Without all the casting?

Code:
static void Main(string[] args){

     string[] text = File.ReadAllLines("test.txt");
     char[] help;

     for (int i = 0; i < text.Length; i++) {

         help = text[i
...