Do you can try this ?
or look more here
win form c# -> Change language of WinForm with resource
using System.Globalization;
using System.Threading;
//LanguageString sample
String languageString = "fr-FR";
//Apply new language
Thread.CurrentThread.CurrentUICulture = new CultureInfo(languageString);
Application.Run(new Form());
asp.net c# -> http://forums.asp.net/t/1244851.aspx/1
protected override void InitializeCulture()
{
Thread.CurrentThread.CurrentUICulture = new CultureInfo("en-GB");
Thread.CurrentThread.CurrentCulture = new CultureInfo("en-GB");
base.InitializeCulture();
}