Forbidden Characters for Naming Controls.

I was wondering if anyone knows what the forbidden characters are when naming ASP.Net Webform Controls.  I have figured out by error that # is not acceptable.  What are the others?

I have used Path.GetInvalidFileNameChars() and filter out the 23 invalid Windows reserved names.  I still get errors from certain characters when creating controls on the fly based off application variables.

Any insight into this would be greatly appreciated.

Thanks.