C# - Prevent Thread.CurrentThread.CurrentCulture To Switch To The Default Browser Value After Setting It Manually?

In my current application I want to implement ASP.Net localization with global resources. I have the problem, that after changing the CurrentThread.CurrentUICulture and CurrentThread.CurrentCulture and changing to another page, these values are overwritten by the browser default values.

I have a DropDownList that enables a selection between different languages. In the ItemChanged Event I store the culturename in the session, redirect to my defaultpage and use this code

protected override void InitializeCulture()
{
System.Threading.Thread.CurrentThread.CurrentUICulture = new CultureInfo("de-DE");
System.Threading.Thread.CurrentThread.CurrentCulture = new CultureInfo("de-DE");
base.InitializeCulture();
}

After switching to another contentpage, that does not override InitializeCulture I'm back to the default browser language. How can I make that persistent?

What options do I have? The following come to my mind:

On every *.aspx page I do implement InitializeCulture I create a new class that derives from System.Web.UI.Page and overrides the InitializeCulture Eventhandler. Every *.aspx page I use derives from it.

Isn't there a more "built-in" way? ASP.net offers such good localization support, so I guess there must be an easier/more efficient way to achieve my goal. Which one is there?