The OS version of image '' is not supported

I am new to dockers and containers. What I am trying to accomplish is to actually have my application running in azure. So far I managed to get a lot done, but the most difficult part I found is to actually get all the versions of ‘image - container - host’ right.

I am building my image against microsoft/dotnet:2.0-sdk-nanoserver-1709

I have been able to publish it to my personal registry in azure. And now I want to create the container:

az container create --resource-group Xxxxx --name xxxproto --image --cpu 1 --memory 1 --registry-username Xxxxx --registry-password xxxxxxx --dns-name-label aci-demo --ports 80 --os-type Windows

And I then get the error: The OS version of image ‘’ is not supported.
So where do I miss the boat? Should I build the image differently? Should I create the container differently?

What I also found is that my image is a size of 438MB, I would expected the image size to be around 50MB.