We have a multi lingual site. The project manager is VERY SEO conscious and requested that we make sure that if you entered the site with a URL without a language defined it would redirect to the page for your default language,
i.e. www.test.com/page1 would redirect to www.test.com/en/page1.

To do this I added the following code into the PreInit event handler of template page:

if (this.CurrentPage != null)
{
string language = this.CurrentPage.LanguageID;
string pageLinkRUL = this.CurrentPage.LinkURL;
if (!string.IsNullOrEmpty(
ConfigurationManager.AppSettings["DispableArabic"]))
{
if (ConfigurationManager.AppSettings["DispableArabic"].ToLower() == "true"
&& language == "ar")
{
language = "en";
pageLinkRUL = pageLinkRUL.Replace("=ar", "=en");
}
}
if (!Request.RawUrl.StartsWith("/" + language))
{
Response.Clear();
Response.StatusCode = 301;
Response.Status = "301 Moved Permanently";
Response.AddHeader("Location", pageLinkRUL);
Response.End();
}
} 

This code works fine except when you are looking at previous versions of page. If you go into the Version List tab and select a previous version of the page and then press the View tab you get the following exception:

[NullReferenceException: Object reference not set to an instance of an object.]

EPiServer.Web.PageExtensions.ContextMenu.SetupOnPageEdit() +88
EPiServer.Web.PageExtensions.ContextMenu.RegisterMenuScripts(Object sender, EventArgs e) +119
System.EventHandler.Invoke(Object sender, EventArgs e) +0
System.Web.UI.Control.OnInit(EventArgs e) +99
System.Web.UI.Page.OnInit(EventArgs e) +9
EPiServer.PageBase.OnInit(EventArgs e) +316
System.Web.UI.Control.InitRecursive(Control namingContainer) +321
System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +834

When I first did some investigation I noticed that the CurrentPage property of the page was not being populated, so I had to add some code in various places to make sure it would not throw exceptions.

I suspect that the above exception is due to the same issue, however I'm not sure how to get around it? Am I doing the right thing in the redirection code, or should I do it in a different way and that would not cause this issue?

Any ideas or suggestions would be gratefully received.

Jim