Powershell Split function not working in VSTS Release pipeline - powershell

Question

I have written a powershell script which takes multiple webapps(comma separated) as input.
I am splitting these webapps using powershell split function and configuring webapps by traversing each one of them using for-each loop.
Everything works fine in Powershell editor but when I configure the same script to VSTS release pipeline , split function doesn't work and which results in failure.
Input : devopstestwebapp1,devopstestwebapp2
Code : $WebAppName = $WebAppName.Split(',')
Output (After Split) : devopstestwebapp1 devopstestwebapp2
Error : The Resource 'Microsoft.Web/sites/devopstestwebapp1
devopstestwebapp2' under resource group 'DevOpsResourseGroup' was not found.
Following is my powershell script
# Parameters
param (
[Parameter(Position=0,mandatory=$true)]
[string] $AADAppID,
[Parameter(Position=1,mandatory=$true)]
[string] $AADKey,
[Parameter(Position=2,mandatory=$true)]
[string] $TenantId,
[Parameter(Position=3,mandatory=$true)]
[string] $ResourceGroupName,
[Parameter(Position=4,mandatory=$true)]
[string] $ServerName,
[Parameter(Position=5,mandatory=$true)]
[string] $RGLocation,
[Parameter(Position=6,mandatory=$true)]
[string] $WebAppName,
[Parameter(Position=7,mandatory=$true)]
[string] $SubscriptionName
)
# Connect to Azure
$ssAADKey = ConvertTo-SecureString $AADKey -AsPlainText -Force
$psCredential = New-Object System.Management.Automation.PSCredential($AADAppID, $ssAADKey)
Connect-AzureRmAccount -ServicePrincipal -Credential $psCredential -Subscription $SubscriptionName -TenantId $TenantId
write-host $WebAppName
$WebAppName = $WebAppName.Split(',')
write-host $WebAppName
Foreach ($servicename in $WebAppName)
{
write-host $servicename
  }

Answer 1

Below works perfectly with VSTS powershell task :
Store app name in variable :
$WebAppName = '$(WebAppName)'
write-host $WebAppName
foreach($servicename in $WebAppName.Split(','))
{
write-host $servicename
}
Output :
2019-04-22T11:02:02.7680996Z devopstestwebapp1,devopstestwebapp2,devopstestwebapp3
2019-04-22T11:02:02.7737101Z devopstestwebapp1
2019-04-22T11:02:02.7750490Z devopstestwebapp2
2019-04-22T11:02:02.7765756Z devopstestwebapp3

Answer 2

The problematic line is this one:
$WebAppName = $WebAppName.Split(',')
You are reassigning the result of split to the same variable $WebAppName which has been declared as a string in the parameter list. So the array result of Split will be cast to a string, not an array anymore.
The solution is to assign the result of split to a new variable:
$WebAppNameSplit = $WebAppName.Split(',')