How to override web.config customErrors settings at runtime?

I have the following code in the web.config file for my ASP.NET C# app that's hosed on Azure:

<!-- Turn on Custom Errors -->
<!-- Switch the mode to RemoteOnly for Retail/Production -->
<!-- Switch the mode to On for to see error pages in the IDE during development -->
<customErrors mode="On" defaultRedirect="ErrorPage.aspx">
   <error statusCode="403" redirect="ErrorPage403.aspx"/>
   <error statusCode="404" redirect="ErrorPage404.aspx"/>
</customErrors>

This works great for errors when I'm hitting my site site natively (http://ipredikt.com/ErrorPage.aspx), but I also have a Facebook version of the app in which all of the pages use a different MasterPage and hence a different URL (http://ipredikt.com/ErrorPageFB.aspx).

Is it possible to modify the customError redirect values at runtime when I'm running in Facebook app mode, as if I had the following settings in web.config:

<customErrors mode="On" defaultRedirect="ErrorPageFB.aspx">
   <error statusCode="403" redirect="ErrorPage403FB.apx"/>
   <error statusCode="404" redirect="ErrorPage404FB.apx"/>
</customErrors>

I don't think I can set this at the Application scope since it's individual pages in my app that have knowledge of whether they are running in Faceb开发者_如何转开发ook mode.

Hi I think what you can do is make another redirect inside your custom error page acording to the referrer - Request.UrlReferrer sometime the referrer is null so make sure you deal with that

So here's a brute force solution. I'm using this on the page for the non-Facebook mode 404 errors:

  protected override void OnInit(System.EventArgs e)
  {         
     // If the user tries, for example, to navigate to" /fb/foo/bar
     // then the Request.Url.Query will be as follows after the 404 error: ?aspxerrorpath=/fb/foo/bar
     string queryString = Request.RequestContext.HttpContext.Request.Url.Query;

     string[] str = queryString.Split('=');

     if (str.Length > 0)
     {
        string[] str2 = str[1].Split('/');

        if (str2.Length > 1)
        {
           string test = str2[1].ToLowerInvariant();

           if (test == "fb")
           {
              string pathAndQuery = Request.RequestContext.HttpContext.Request.Url.PathAndQuery;
              string absolutePath = Request.RequestContext.HttpContext.Request.Url.AbsolutePath;

              string mungedVirtualPath = pathAndQuery.Replace(absolutePath, "/ErrorPage404FB.aspx");

              Response.Redirect(mungedVirtualPath);
           }
        }
     }

     base.OnInit(e);
  }

Hardly ideal, but it works.

"Facebook mode" seems like something you could track in Session, which would be accessible in ErrorPage.aspx to trigger a transfer to ErrorPageFB.aspx.

Update - you can clean up your brute-force solution quite a bit by using Request.QueryString:

protected override void OnInit(System.EventArgs e)
{         
    // If the user tries, for example, to navigate to" /fb/foo/bar
    // then the Request.Url.Query will be as follows after the 404 error: ?aspxerrorpath=/fb/foo/bar
    var requestedPath = Request.RequestContext.HttpContext.Request.QueryString["aspxerrorPath"];

    if (requestedPath.StartsWith("/fb/", StringComparison.OrdinalIgnoreCase))
    {
        var requestedUrl = Request.RequestContext.HttpContext.Request.Url;
        var pathAndQuery = requestedUrl.PathAndQuery;
        var absolutePath = requestedUrl.AbsolutePath;

        var mungedVirtualPath = pathAndQuery.Replace(absolutePath, "/ErrorPage404FB.aspx");

        Response.Redirect(mungedVirtualPath);
    }

    base.OnInit(e);
}

Does Request.RequestContext.HttpContext.Request actually return a different instance than simply Request?

The easy way to do it is using session but if you don't use session on you website you can always use cookie and when the user arrive to the error page examine the cookie and decide if you want to redirect him to a new error page