What happens between Global.asax and MasterPage?

Question

I am starting a multilanguage effort. In Global.asax.cs, method Application_BeginRequest(), a cookie is read and CurrentUICulture is set to en-US. However, in MyPage.aspx the value has surprisingly changed to nl.

Now this web site I inherited, and is medium-sized and has a fairly complex menu system. Also, it maintains a user table with a field for Preferred Language with values like nl, but I could not find (yet) in the code where this sets CurrentUICulture from that user table.

This is a page with a MasterPage, so I looked over there. I set a debug breakpoint in the first page event in MasterPage.Page_Init(), and in the Immediate Window I inspected System.Threading.Thread.CurrentThread.CurrentUICulture.Name. Value is: 'nl'. I am completely puzzled.

My question is: what code can possibly execute between Global.asax.cs, Application_BeginRequest(), and MasterPage.Page_Init()?

Answer 1

The Application_BeginRequest() handler is the first step in the Asp.Net life cycle. Look here:

https://learn.microsoft.com/en-us/iis/application-frameworks/building-and-running-aspnet-applications/aspnet-integration-with-iis

When a handler is executing (which is your page), it has its own life cycle:

https://learn.microsoft.com/en-us/previous-versions/ms178472(v=vs.140)?redirectedfrom=MSDN

And this documentation says:

Start

In the start stage, page properties such as Request and Response are set. At this stage, the page also determines whether the request is a postback or a new request and sets the IsPostBack property. The page also sets the UICulture property.

When the available events are checked, we see:

PreInit

Raised after the start stage is complete and before the initialization stage begins.

Therefore; it seems that the earliest stage you can change the UICulture is the PreInit stage. The most appropriate place however, is the InitializeCulture method which serves this specific purpose:

public partial class _Default : Page
{
    protected override void OnPreInit(EventArgs e)
    {
        base.OnPreInit(e);

        HttpCookie languageCookie = Request.Cookies["lang"];
        if (languageCookie != null)
        {
            if (languageCookie.Value == "en")
            {
                base.Culture = base.UICulture = CultureInfo.GetCultureInfo("en-US").Name;
            }
        }
    }

    protected override void InitializeCulture()
    {
        // Or do it here. This is more appropriate.
    }
    ...
    ...
}

EDIT:

Despite being shared accross multiple pages, the culture information should not be set in the Master Page's event handlers, because as can be seen in the following trace output, when a page uses a master page, the master page is interpreted as a control of the page and the Page_Load event of this master page is executed during LoadControls() which is executed after the Page's Page_Load handler.

I also want to mention the tracing feature here. By enabling tracing, it is possible to see a lot of information about the page's execution process, its children, all the timings, headers etc.:

In the web.config file, under <system.web>:

<trace pageOutput="true" requestLimit="10" enabled="true" localOnly="true" traceMode="SortByTime" mostRecent="true"/>

Or read here for the <system.webServer> equivalent:

https://learn.microsoft.com/en-us/iis/configuration/system.webserver/tracing/

Control Tree
Control UniqueID    Type    Render Size Bytes (including children)  ViewState Size Bytes (excluding children)   ControlState Size Bytes (excluding children)
__Page  ASP.default_aspx    1104    0   0
    ctl00   ASP.masterpage_master   1104    0   0
        ctl00$ctl02 System.Web.UI.LiteralControl    68  0   0
        ctl00$ctl00 System.Web.UI.HtmlControls.HtmlHead 48  0   0
            ctl00$ctl01 System.Web.UI.HtmlControls.HtmlTitle    29  0   0
            ctl00$head  System.Web.UI.WebControls.ContentPlaceHolder    6   0   0
                ctl00$head$ctl00    System.Web.UI.LiteralControl    6   0   0
        ctl00$ctl03 System.Web.UI.LiteralControl    14  0   0
        form1   System.Web.UI.HtmlControls.HtmlForm 954 0   0
            ctl00$ctl04 System.Web.UI.LiteralControl    21  0   0
            ctl00$ContentPlaceHolder1   System.Web.UI.WebControls.ContentPlaceHolder    291 0   0
                ctl00$ContentPlaceHolder1$ctl00 System.Web.UI.LiteralControl    198 0   0
                ctl00$ContentPlaceHolder1$hdn1  System.Web.UI.WebControls.HiddenField   91  0   0
                ctl00$ContentPlaceHolder1$ctl01 System.Web.UI.LiteralControl    2   0   0
            ctl00$ctl05 System.Web.UI.LiteralControl    18  0   0
        ctl00$ctl06 System.Web.UI.LiteralControl    20  0   0