Web Forms :: FileUpload Validate File Size Before Upload Starts Not Working

I do not want to change the default settings for file upload, 4Mb is more than enough for the project I'm working on. After quite a bit of searching I found two approaches that were purported to work but neither one is preventing the "Maximum request length exceeded" error. The first approach[see ref. #1 below] performs validation with a custom validator and in code behind on the page that contains the FileUpload control. It doesn't work. The second approach [see ref #2 below] performs validation in the Application_BeginRequest event in Global.asax. The author stated that validation must be handled by this event. Quoting: "The way to get past is to use your Application_BeginRequest event to handle the problem.. This event takes place for each request to your application BEFORE the data has been completely uploaded. Here you can check for the content length of the request and then redirect to the some error page or the same page with some value in session or query string so that the page can show appropriate message to the user." Here is my code from Golbal.asax based on the above. As noted, this approach doesn't work either.

protected void Application_BeginRequest(object sender, EventArgs e)
{
const int maxFileSize = 4 * 1000000; // Slightly less than 4Mb
if (Request.ContentLength > maxFileSize)
{
Response.Redirect("~/FileUploadError.aspx");
}
}

One comment by a reader of the Global.asax approach was that the value returned by Request.Content.Length would include everything on the page, i.e. viewstate, image and text content, etc. I suppose one work-around would be to set the limit higher in web.config but validate for max. file size in code behind, but that seems kind of silly because I'm manipulating the uploaded files (images) to reduce the size anyway; storage space isn't the issue, performance is. Has anyone managed to solve this poblem?