The REST client here createorupdate shows how to create a network profile, but there doesn't seem to be any corresponding code in Azure Fluent. When creating a Container Instance in Azure CLI, it automatically creates a Network Profile, but the Fluent class for Network Profiles doesn't seem to do anything. So how can you create a network profile in Fluent?
What you find in Network Profiles is a model for container service, not an available interface for the network. What you need is the interface here:
CreateOrUpdateWithHttpMessagesAsync(String, String, NetworkProfileInner, Dictionary<String,List>, CancellationToken)
This is the right one for Network.