Script to demonstrate hashtable merging in powershell and updating web applications in azure

update-AppSettings.ps1

param($websitename = 'TEst' ,$resourceGroup = 'SchuTest',$slot = 'production', $appSettings ='{"AppSettings:testkey1": "45test","AppSettings:TestId": "This is a Test Key 28"}')
#https://stackoverflow.com/questions/8800375/merging-hashtables-in-powershell-how
Function Merge-Hashtables([ScriptBlock]$Operator) {
    $Output = @{}
    ForEach ($Hashtable in $Input) {
        If ($Hashtable -is [Hashtable]) {
            ForEach ($Key in $Hashtable.Keys) {$Output.$Key = If ($Output.ContainsKey($Key)) {@($Output.$Key) + $Hashtable.$Key} Else  {$Hashtable.$Key}}
        }
    }
    If ($Operator) {ForEach ($Key in @($Output.Keys)) {$_ = @($Output.$Key); $Output.$Key = Invoke-Command $Operator}}
    $Output
}
try {
   foreach($website in $websiteName)
   { 
       ConvertFrom-Json $appSettings -ErrorAction Stop
        #it is expected that the app settings is a string representation of a hashtable that is writtin in Json.  So that it can be converted to a powershell hashtable during runtime
        $newAppSettings = $appSettings | convertfrom-json 
        $newAppSettingsHash = @{}
        $newAppSettings.psobject.properties | ForEach-Object { $newAppSettingsHash[$_.Name] = $_.Value } 
        $Application = get-azurermwebappslot -Name $website -ResourceGroupName $resourceGroup -Slot $slot
        $ExistingSettings = $Application.siteconfig.AppSettings
        $appSettingsHash = @{}
        foreach($k in $ExistingSettings)
        {
            $appSettingsHash[$k.name] = $k.value
        }
        #https://stackoverflow.com/questions/8800375/merging-hashtables-in-powershell-how
        $hashtable = $newAppSettingsHash, $appSettingsHash | Merge-Hashtables {$_[0]}
        $results = Set-AzureRmWebAppSlot -AppSettings $hashtable -name $website -ResourceGroupName $resourceGroup -slot $slot
        $r = $results.SiteConfig.AppSettings
        Write-Output $r
    }
} 
catch 
{
    Write-Error "$appsettings must be in JSON format"
}