How to get existing resource name from resource group or a subscription?

### Issue Details
I want to populate the parameters allowed list with values, taken from the current resource group.
To be clear - i want to place a virtual machine to virtual network subnet but dont want to enter vNet name manually. I find a way to get resourcegroup id, resource group name, subscription id but it seems what there is no way to get a list of objects from here - only if i know resource name, please tell me - it is possible at all?

The issue concerns discovering existing Azure resources for a deployment parameter, specifically selecting a virtual network subnet from a resource group or subscription. Start by reviewing Azure template parameter and resource-reference capabilities; done means establishing whether an allowed-values list can be populated without manually entering the resource name.

Written by the indexing model from the issue text.