both solutions gave error, so i thought may be there was error in file (as i was already writing values in file on starting)
So i gave app a blank file, then save values to file with a BUTTON. After this no error was there on reading file.
spnFontSize.SelectedIndex =lstSettings.Get(0) 'this simply worked
used this code for saving
lstSettings.Clear
lstSettings.Add(spnFontSize.SelectedIndex)
lstSettings.Add(spnFcolor.SelectedIndex)
lstSettings.Add(spnBcolor.SelectedIndex)
File.WriteList(File.DirInternal, "settings.txt", lstSettings)
used this code for reading lstSettings.Clear
lstSettings=File.ReadList(File.DirInternal , "settings.txt")
spnFontSize.SelectedIndex =lstSettings.Get(0)
spnFcolor.SelectedIndex =lstSettings.Get(1)
spnBcolor.SelectedIndex =lstSettings.Get(2)