Hey there,
In order to convert all of your ANSI encoded files to utf-8, you first need to get a list of your files in folder. After that you could use this code snippet..
StreamReader sr = new StreamReader(infile);
StreamWriter sw = new StreamWriter(outfile, false, Encoding.UTF8);
sw.WriteLine(sr.ReadToEnd);
sw.Close();
sr.Close();
Hope i helped. :)