You can write a console application to process your Setting.txt
invoke your console application in your pre-build event
replace.exe "servera" "serverb" "....\Settings.txt" --for example
in your console application code
static void Main(string[] args)
{
FileStream fs = new FileStream(args[3],FileMode.OpenOrCreate);
StreamReader sr = new StreamReader(fs);
StreamWriter sw = new StreamWriter(fs);
string content = sr.ReadToEnd();
content = content.Replace(args[0], args[1]);
fs.Position = 0;
sw.Write(content);
}