Get and Set File Associations

function Set-FileAssociation {
    Param (
        [Parameter(Mandatory)][string[]]$Extension,
        [Parameter(Mandatory)][ValidateScript({ Test-Path $_ })][string]$Path
    )
    foreach ($e in $Extension) {
        $e = $e -replace '\A\.?', '.'
        $fileType = (cmd /c "assoc $e") -split '='
        if ($fileType.Count -eq 2) {
            $fileType = $fileType[1]
            cmd /c "ftype $fileType=""$Path"" ""%1"""
        } else {
            Write-Error "Could not determine association for extension $e."
        }
    }
}

function Get-FileAccociation {
    param ([string]$FileType = '*')
    cmd /c ftype | Select-String -Pattern '(.*?)=(.*)' | % { [pscustomobject]@{ FileType = $_.Matches[0].Groups[1].Value; Association = $_.Matches[0].Groups[2].Value } } | ? FileType -Like $FileType
}