VSTS Azure powershell : No default subscription has been designated - powershell

Question

I'm trying to run some azure powershell commands as part of my Visual Studio Team Services build using Azure Resource Manager.
It gives me the following error:
No default subscription has been designated. Use Select-AzureSubscription -Default to set the default subscription.
The commands I'm trying to run:
$website = Get-AzureWebsite | where {$_.Name -eq 'my-website'}
Write-Output ("##vso[task.setvariable variable=DeployUrl;]$website.HostNames")
When I tried to run it locally, I had to call
Add-AzureAccount
Select-AzureRmSubscription -SubscriptionName "Visual Studio Premium with MSDN"
to get it working, but it is not possible in the VSTS build.
UPDATE:
I've configured it to use the azure classic mode instead of resource manager, at it works. I don't think that it is a feasible solution for production as azure classic mode is obsolete.

Answer 1

Since you are using Azure Resource Manager, please check the things below:
Make sure "Azure Resource Manager" service endpoint is added correctly.
Use "Get-AzureRmWebApp" command instead of "Get-AzureWebsite" command just as bmoore mentioned.
I have tested it at my side, it works correctly.
My PowerShell script:
$website = Get-AzureRmWebApp | where {$_.Name -eq 'eddieapp0930'}
Write-Host $website.HostNames
Run from "Azure PowerShell Script" task:

Answer 2

Thank you for your question.
If you are using service manager mode(classic mode), the correct cmdlet is:
Add-AzureAccount
Get-AzureSubscription -SubscriptionName “name” | Select-AzureSubscription
If you are using Resource Manager, the correct cmdlet is:
Login-AzureRmAccount
Get-AzureRmSubscription –SubscriptionName "name" | Select-AzureRmSubscription
or just use -SubscriptionId instead of -SubscriptionName.
More information about ASM and ARM, please refer to the link below:
https://azure.microsoft.com/en-us/documentation/articles/resource-manager-deployment-model/
If you still have questions, welcome to post back here. Thanks.