My reading of the specification leads me to the conclusion that you can
have just one itemprop attribute per element but it can have more than
one value.
"Every HTML element may have an itemprop attribute specified... The
itemprop attribute, if specified, must have a value that is an
unordered set of unique space-separated tokens that are
case-sensitive, representing the names of the name-value pairs that it
adds. The attribute's value must have at least one token."
http://www.whatwg.org/specs/web-apps/current-work/multipage/microdata.html#names:-the-itemprop-attribute
You might try the nu validator or a microdata parser to test your code
and make sure you're getting the output you expect.
So instead of <span itemprop="name" itemprop="description">
you would use <span itemprop="name description">
Google's Rich Snippet Testing Tool may not be able to handle multiple itemprop values, yet, though.
I don't know what that asp will generate, but I think you want output more like this:
<a href="/" itemprop="url"><span itemprop="manufacturer">The Name</span></a>
In order to get access to the text content of the link you add an extra span. The value of an a element will always just be the value of its href attribute. Adding an extra span to get access to the text content of a link is a common pattern.