参考资料:http://hi.baidu.com/lsheshang/blog/item/c63a7889a81399b20e24445e.html

BasePage.cs

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Runtime.Remoting.Contexts;
using System.Threading;
using System.Globalization;

/// <summary>
/// Summary description for BasePage
/// </summary>
public class BasePage : System.Web.UI.Page
{
    public BasePage()
    {
        //
        // TODO: Add constructor logic here
        //
    }

    protected override void InitializeCulture()
    {
        string s = (string)Context.Profile.GetPropertyValue("LanguagePreference");
        if (!string.IsNullOrEmpty(s) && (s != "Auto"))
        {
            //UICulture - 决定了采用哪一种本地化资源，也就是使用哪种语言
            //Culture - 决定各种数据类型是如何组织，如数字与日期
            Thread.CurrentThread.CurrentUICulture = new CultureInfo(s);
            Thread.CurrentThread.CurrentCulture = CultureInfo.CreateSpecificCulture(s);
        }
    }
}

MasterPage.master.cs

using System;
using System.Data;
using System.Configuration;
using System.Collections;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Runtime.Remoting.Contexts;

public partial class MasterPage : System.Web.UI.MasterPage
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void RadioButtonList1_SelectedIndexChanged(object sender, EventArgs e)
    {
        string language = RadioButtonList1.SelectedValue.Trim();
        Profile.LanguagePreference = language;
        Response.Redirect(Request.Url.AbsolutePath);
    }
}

Default.cs

public partial class _Default : BasePage
{
    protected void Page_Load(object sender, EventArgs e)
    {
    }
}

Web.config

<configuration>
    <system.web>
        <anonymousIdentification enabled="true"/>
        <profile>
            <properties>
                <add name="LanguagePreference" type="string"
                     defaultValue="Auto" allowAnonymous="true" />
            </properties>
        </profile>
    </system.web>
</configuration>