When moving your pages from one place to another it is very tempting to handle old inlinks by creating a simple Response.Redirect( sNewPage, true );
This sure will work, but this type of redirect is a 302 and is meant for temporary relocations of pages. But your pages are permanently moved and therefore you should use a 301 Moved Permanently status code. This should preserve your search engine rankings for that particular page.
To solve it you could install some sort of redirect filter(ISAPI dll). I was looking into those type of solutions and found IISMods URL Rewrite Filter for IIS.
Such a solution is very flexible and since it is a IIS filter it is possible to rewrite URL:s for all kind of filetypes, not only for aspx pages but say images (ex http://www.hello.com/*.gif could be transferred to http://www.hello.com/test/*gif ).
It is however not possible for everyone to install a ISAPI filter on their website, therefore I here present a solution on how you can achieve 301 redirects with pure ASP.NET code instead.
In your old page you can write code such as
private void Page_Load(object sender, System.EventArgs e)
{
Response.Status = "301 Moved Permanently";
Response.AddHeader("Location","http://www.aspcode.net/newpage");
}
For me who wanted to redirect all calls to http://kbmentor.aspcode.net/whatever/it/could/be/foo.aspx to http://www.aspcode.net/articles/whatever/it/could/be/foo.aspx took and didn't have to think about pictures, cause they were "base" linked with the application took the idea one step further.
I created a new web application to install on kbmentor.aspcode.net. Basically it only contains a global.asax which handles Application_BeginRequest like this:
protected void Application_BeginRequest(Object sender, EventArgs e)
{
string sOldPath = HttpContext.Current.Request.Path.ToLower();
string sPage = "http://www.aspcode.net/articles/" + sOldPath;
Response.Clear();
Response.Status = "301 Moved Permanently";
Response.AddHeader("Location",sPage);
Response.End();
}