public static ArrayList GetAllCountires()
        {
            foreach (CultureInfo ci in CultureInfo.GetCultures(CultureTypes.AllCultures & ~CultureTypes.NeutralCultures))
            {
                RegionInfo ri = new RegionInfo(ci.LCID);
                countryList.Add(ri.EnglishName);
            }

            return countryList;
        }

You can get all countries list by this method.
Also you can find some details for countries like;
- original name,
- three letter ISO region name,
- three letter WINDOWS region name, 
- currency symbol
etc..

Get Countries List

list, c

C#