Write out XML as a file

[JimmyFo]

I have a string inside a VB.Net codebehind for an ASP.Net page. I would like to write this XML string out as a new XML file, specifying the file name, etc - the user should be prompted with the usual open/save/cancel dialogue. I assume I would need some sort of Response.Write or WriteFile, but since it's not saved locally, how do I cast that string as a download file and present it to the user? The only way I can find is by mapping to a local file.

Thanks,
James