UrlEncode/UrlDecode in C#

Use HttpUtility.UrlEncode(string url) & HttpUtility.UrlDecode(string url) respectively.

You need the reference to System.Web.

InfoPath: Retrieving URL Path without Code

Create a data field in Infopath, add a hidden control with the following formula as the default value:
substring-before(substring-after(/processing-instruction(), 'href="'), '"')

The value returned is: http://servername/DocLibName/Forms/template.xsn

Not the perfect solution because I would also like to know the folder in which the "New Form" was called.