## Set a SMO Server object to the default instance on the local computer.
CD SQLSERVER:SQLlocalhostDEFAULT
$srv = get-item .

## Specify the database to extract to a DAC.
$dbname = "MyDB"

## Specify the DAC metadata.
$applicationname = "MyApplication"
$version = "1.0.0.0"
$description = "This DAC defines the database used by my application."

## Specify the location and name for the extracted DAC package.
$dacpacPath = "C:MyDACsMyApplication.dacpac"

## Extract the DAC.
$extractionunit = New-Object Microsoft.SqlServer.Management.Dac.DacExtractionUnit($srv, $dbname, $applicationname, $version)
$extractionunit.Description = $description
$extractionunit.Extract($dacpacPath)