Question

I am following the code over here https://web.archive.org/web/20211020203216/https://www.4guysfromrolla.com/articles/072810-1.aspx

to redirect http://somesite.com to http://www.somesite.com

protected void Application_BeginRequest(object sender, EventArgs e)
{
   if (Request.Url.Authority.StartsWith("www"))
      return;

   var url = string.Format("{0}://www.{1}{2}",
               Request.Url.Scheme,
               Request.Url.Authority,
               Request.Url.PathAndQuery);

   Response.RedirectPermanent(url, true);
}

How can I use this code to handle situations where http://abc.somesite.com should redirect to http://www.somesite.com

Answer 1

1. If you don’t know what the values will be ahead of time, you can use substring with indexof for the Url path to parse out the value you want and replace it.

2. If you do know what it is ahead of time, you can always just do Request.Url.PathAndQuery.Replace(“abc”, “www”);

You can also do a dns check as @aceinthehole suggested after you have parsed what you need to make sure you haven’t made any mistakes.

assuming you have a string like http://abc.site.com and you want to turn abc into www then you could do something like.

string pieceToReplace = Request.Url.PathAndQuery.substring(0, Request.Url.PathAndQuery.IndexOf(".") + 1);

//here I use the scheme and entire url to make sure we don't accidentally replace an "abc" that belongs later in the url like in a word "GHEabc.com" or something.
string newUrl = Request.Url.ToString().Replace(Request.Url.Scheme + "://" + pieceToReplace, Request.Url.Scheme + "://www");

Response.Redirect(newUrl);

p.s. I don’t remember if the Request.Url.Scheme already has the “://” in it or not so you will need to edit accordingly.