[powershell] How to install .MSI using PowerShell

After some trial and tribulation, I was able to find all .msi files in a given directory and install them.

foreach($_msiFiles in 
($_msiFiles = Get-ChildItem $_Source -Recurse | Where{$_.Extension -eq ".msi"} |
 Where-Object {!($_.psiscontainter)} | Select-Object -ExpandProperty FullName)) 
{
    msiexec /i $_msiFiles /passive
}