VirtualPathProvider and mimetype (for RESTful applications)

[forge1968]

I want to handle URLs like this on my IIS site:

http://localhost/myapp/REST/foo/1 ('REST/foo/1' doesn't exist - I'll
dynamically create the content).

I have implemented my own VirtualPathProvider and VirtualFile classes
to do this. However, the mimetype of the response is 'application/
octet-stream'. I want it to be 'text/xml'.

Changing HttpContext.Current.Response.ContentType does not affect the
response.

The only way I've found is to append a '.xml' to the URL:

http://localhost/myapp/REST/foo/1.xml

This is *really* ugly....

How can I change the response mimetype from within my custom
VirtualFile class?

I'm using .NET 2 and IIS 5 & 6.

Thanks in advance for any help!

M.D.