IIS urlMappings redirects and SEO - asp.net

Question

I am using IIS7 and urlMappings to map some urls to actual pages.
Example:
<urlMappings>
<!-- Remap friendly urls to actual pages: -->
<add url="~/help/" mappedUrl="~/content/help/help.aspx" />
<add url="~/news/" mappedUrl="~/content/news/default.aspx" />
</urlMappings>
This works great if the url has a trailing '/' , example:
http://www.mysite.com/news/
But I get page not found error if I do this:
http://www.mysite.com/news
I could add an extra entry without the trailing '/' so that both map to the same page, but I don't want to do this for SEO (would think it is duplicate content).
Is it possible to get the urlMappings to redirect?
For example, something like this:
<add url="~/help" redirect="~/help/" />
If not, what would be the best way of doing this?
Do you think google would really penalize
http://www.mysite.com/news/
http://www.mysite.com/news
as duplicate?

Answer 1

Here is my work around:
I add both entries, with and without trailing '/', to the urlMappings in web.config
<urlMappings>
<!-- Remap friendly urls to actual pages: -->
<add url="~/help/" mappedUrl="~/content/help/help.aspx" />
<add url="~/help" mappedUrl="~/content/help/help.aspx" />
</urlMappings>
Then in the page itself add the following code on page_load:
Dim mappedUrl as string = "/help"
If Request.RawUrl.EndsWith(mappedUrl) Then
Response.RedirectPermanent(String.Format("~{0}/", mappedUrl))
End If
This will permanently redirect and calls to the mapped page without a trailing '/' to the same page with a trailing '/'