Determining what Url the user originally entered to visit a web page after redirection
<p>Currently, I'm just using clientside Javascript (<code>location.href</code>), but I am wondering if there is a way in Asp.Net to figure out the URL the user originally entered (assume I did not change it myself via 301), or at least to track it in a simple and reliable manner.  As I am using my own implementation of URL rewriting via the global.asax (e.g. <code>Context.RewritePath</code>), this is not an easy task, particularly since I don't want to touch it too much.</p>

<p><b>Example</b></p>

<pre><code>Global.asax:
    public override void Init()
    {
        base.Init();
        this.BeginRequest += new EventHandler(Global_BeginRequest);
    }

    void Global_BeginRequest(object sender, EventArgs e)
    {
        if (VARIOUSCONDITIONS) Context.RewritePath("SOMEURL");
    }

SomePage.aspx.cs

    protected void Page_Init(object sender, EventArgs e)
    {
        //Request.RawUrl is equal to "SOMEURL", as 
        //are other properties that store the URL.
    }
</code></pre>
