I've been looking around trying to find a .NET release of the eBay Shopping API. Is there any?
The link you provided states:
Supported Features
Formats: XML, SOAP, Name Value, JSON
Protocols: HTTP GET (REST) and POST"
It's a web service. You don't need a particular ".Net API". Just make a call to the webpage and handle the return value.
Example using information on this page
var xml = http://open.api.ebay.com/shopping?callname=FindProducts&responseencoding=XML&appid=YourAppId&siteid=0&QueryKeywords=harry%20potter&AvailableItemsOnly=true&MaxEntries=2&version=787
//parse the xml...
Of course you would need to use valid data. If you try using this as is you'll get an error xml response:
<FindProductsResponse xmlns="urn:ebay:apis:eBLBaseComponents">
<Timestamp>2012-09-09T07:03:43.405Z</Timestamp>
<Ack>Failure</Ack>
<Errors>
<ShortMessage>Application ID invalid.</ShortMessage>
<LongMessage>Application ID invalid.</LongMessage>
<ErrorCode>1.20</ErrorCode>
<SeverityCode>Error</SeverityCode>
<ErrorClassification>RequestError</ErrorClassification>
</Errors>
<Build>E789_CORE_BUNDLED_15285085_R1</Build>
<Version>789</Version>
</FindProductsResponse>
However the whole point of this is that you send eBay some data via a query string and they return you xml.
This is the url used in the example above.