Manage Sharepoint element property bag from powershell

WorkWithPropertyBag.ps1

if ((Get-PSSnapin "Microsoft.SharePoint.PowerShell" -ErrorAction SilentlyContinue) -eq $null) {
	Add-PSSnapin "Microsoft.SharePoint.PowerShell"
}

$web = Get-SPWeb 'http://win13a/sites/dev'
$web.AllProperties['PropertyName'] = '312'
$web.Update()


$webApp = Get-SPWebApplication 'http://win13a/'
$webApp.Properties['PropertyName'] = '312'
$webApp.Update()