How to generate a Google Merchant shopping feed in dotnet controller

Question

I'm trying to create a GoogleMerchantController that returns an xml feed to upload to Google Merchant Center but when I connect the url it always says that price, availability and image_link are missing.

Here is an example of the generated xml

<?xml version="1.0" ?>
<rss version="2.0" xmlns:g="https://base.google.com/ns/1.0">
<channel>
<title>QOSMO</title>
<description>Google Merchant: QOSMO</description>
<link>https://www.qosmo.be</link>
<item>
<g:id>1240628BLK</g:id>
<g:title>Petra flap bag black</g:title>
<g:description>Petra flap bag black</g:description>
<g:link>https://www.qosmo.be/product/petra-flap-bag-black</g:link>
<g:condition>new</g:condition>
<g:price>169,00 EUR</g:price>
<g:image_link>https://www.qosmo.be/media/Shoot%20FW23-24/IMG_9205.JPG</g:image_link>
<g:availability>out of stock</g:availability>
</item>
</channel>
</rss>

Does anyone have an idea what I did wrong?