$connectionName = "AzureRunAsConnection"
$servicePrincipalConnection=Get-AutomationConnection -Name $connectionName  
Add-AzureRmAccount -ServicePrincipal -TenantId $servicePrincipalConnection.TenantId -ApplicationId $servicePrincipalConnection.ApplicationId -CertificateThumbprint $servicePrincipalConnection.CertificateThumbprint 
$functionname="<<FunctionAppName>>"
$resourceGroupName ="<<Resource Group Name>>"
$webApp = Get-AzureRmWebApp -ResourceGroupName $resourceGroupName -Name $functionname
$appSettingList =$webApp.SiteConfig.AppSettings
$appSettings = @{}
ForEach ($kvp in $appSettingList) {
    $appSettings[$kvp.Name] = $kvp.Value
}
$appSettings["AzureWebJobs.<<Function App Name>>.Disabled"] = "true"
$res = Set-AzureRmWebApp -AppSettings $appSettings -ResourceGroupName $resourceGroupName -Name $functionname
Write-Output "Done!"