If you need to reserve static ip address for your VM, follow the commands below:
1. Set static ip:
New-AzureReservedIP -ReservedIPName "postgresql" -Location "West US"
2. Assign static ip, defined above to VM named postgresql –vm
Powershell: Check variable for null
If your working a lot with parameters and inputs you need to check if variables have the right value and are not “null”.
You can check that (check if $variablename has $null as value):