Test-Get-ADUser.ps1

$ADUsers = Get-ADUser -Filter *
$ADUsersHT = @{}
[collections.arraylist]$ADUsersArray = @()
foreach ($aduser in $ADUsers){
    $ADUsersHT.Add($aduser.Samaccountname,$aduser)
    $null = $ADUsersArray.Add($aduser)
}
$ADusersCSV = $ADUsers | ConvertTo-CSV | ConvertFrom-Csv
$ADUsersJSON = $AdusersCSv | ConvertTo-Json | ConvertFrom-Json


$users = @()
for ($i=0;$i -lt 100;$i++){
    $users += $adusers[$(Get-Random -Minimum 0 -Maximum ($ADUsers.Count - 1))].Samaccountname
}

$ADCounter = 0
$ADObjectsCounter = 0
$ADObjectsForeachbreakCounter = 0
$ADObjectsForeachCounter = 0
$ADObjectsWhereCounter = 0
$ADObjectsWhereFirstCounter = 0
$CSVCounter = 0
$CSVWhereCounter = 0
$CSVWhereFirstCounter = 0
$JSONCounter = 0
$JSONForeachbreakCounter = 0
$JSONForeachCounter = 0
$ArrayCounter = 0
$HTCounter = 0
$Counter1
$ADEnCounter = 0
$HTEnCounter = 0
$HTEnCounter2 = 0
$JSONEnCounter = 0
$ADEnObjectsCounter = 0
    foreach ($user in $users){

        #Write-Output "Get-ADUser"
        $ADCounter += Measure-Command {
            Get-AdUser $user} | select -ExpandProperty TotalMilliSeconds

        #Write-Output "Where-Object on original results"
        $ADObjectsCounter += Measure-Command {
            $ADUsers | Where samaccountname -EQ "$user"} | select -ExpandProperty TotalMilliSeconds
        #Write-Output "Foreach method with break on original results"
        $ADObjectsForeachbreakCounter += Measure-Command {
            foreach ($aduser in $ADUsers){
                if ($aduser.samaccountname -eq $user){
                    $aduser
                    break
                }
            }
        } | select -ExpandProperty TotalMilliSeconds
        #Write-Output "Foreach method on original results"
        $ADObjectsForeachCounter += Measure-Command {
            foreach ($aduser in $ADUsers){
                if ($aduser.samaccountname -eq $user){
                    $aduser
                }
            }
        } | select -ExpandProperty TotalMilliSeconds
        #Write-Output "Where method on original results"
        $ADObjectsWhereCounter += Measure-Command {
            $ADUsers.Where({$_.samaccountname -EQ "$user"})} | select -ExpandProperty TotalMilliSeconds
        #Write-Output "Where method on original results"
        $ADObjectsWhereFirstCounter += Measure-Command {
            $ADUsers.Where({$_.samaccountname -EQ "$user"},'First',1)} | select -ExpandProperty TotalMilliSeconds

        #Write-Output "Where-Object on CSV"
        $CSVCounter += Measure-Command {
            $ADUsersCSV | Where samaccountname -EQ "$user"} | select -ExpandProperty TotalMilliSeconds
        #Write-Output "Where method on CSV"
        $CSVWhereCounter += Measure-Command {
            $ADUsersCSV.Where({$_.samaccountname -EQ "$user"})} | select -ExpandProperty TotalMilliSeconds
        #Write-Output "Where method on CSV"
        $CSVWhereFirstCounter += Measure-Command {
            $ADUsersCSV.Where({$_.samaccountname -EQ "$user"},'First',1)} | select -ExpandProperty TotalMilliSeconds

        #Write-Output "Where-Object from JSON"
        $JSONCounter += Measure-Command {
            $ADUsersJSON | Where samaccountname -EQ "$user"} | select -ExpandProperty TotalMilliSeconds
        #Write-Output "Foreach with break on JSON"
        $JSONForeachbreakCounter += Measure-Command {
            foreach ($aduser in $ADUsersJSON){
                if ($aduser.samaccountname -eq $user){
                    $aduser
                    break
                }
            }
        } | select -ExpandProperty TotalMilliSeconds
        #Write-Output "Foreach on JSON"
        $JSONForeachCounter += Measure-Command {
            foreach ($aduser in $ADUsersJSON){
                if ($aduser.samaccountname -eq $user){
                    $aduser
                }
            }
        } | select -ExpandProperty TotalMilliSeconds
        #Write-Output "Where-Object on ArrayList"
        $ArrayCounter += Measure-Command {
            $ADusersArray | Where samaccountname -EQ "$user"} | select -ExpandProperty TotalMilliSeconds

        #Write-Output "$(($ADusersHT.gettype()).name)"
        $HTCounter  += Measure-Command {
            $ADUsersHT["$user"]} | select -ExpandProperty TotalMilliSeconds

        $ADEnObjectsCounter += (measure-command {$ADUsers | where {$_.samaccountname -eq $user -and $_.enabled -eq $true}}).TotalMilliSeconds
        $JSONEnCounter += (measure-command {foreach ($aduser in $ADUsersJSON){
                if ($aduser.samaccountname -eq $user -and $aduser.Enabled -eq $true){
                    $aduser.Enabled
                    break
                }
            }}).TotalMilliSeconds
        $HTEnCounter2 += (measure-command {($ADUsersHT[$user]).enabled -eq $true}).TotalMilliSeconds
        $ADEnCounter +=(measure-command {(Get-ADUser $user).enabled -eq $true}).TotalMilliSeconds
    }


" ======= "
"ADCounter $ADCounter"
"ADObjectsCounter $ADObjectsCounter"
"ADObjectsWhereCounter $ADObjectsWhereCounter"
"ADObjectsWhereFirstCounter $ADObjectsWhereFirstCounter"
"ADObjectsForeachCounter $ADObjectsForeachCounter"
"ADObjectsForeachbreakCounter $ADObjectsForeachbreakCounter"
"CSVCounter $CSVCounter"
"CSVWhereCounter $CSVWhereCounter"
"CSVWhereFirstCounter $CSVWhereFirstCounter"
"JSONCounter $JSONCounter"
"JSONForeachbreakCounter $JSONForeachbreakCounter"
"JSONForeachCounter $JSONForeachCounter"
"ArrayCounter $ArrayCounter"
"HTCounter $HTCounter"
"=="
"ADEnCounter $ADEnCounter"
"ADEnObjects $ADEnObjectsCounter"
"HTEnCounter $HTEnCounter"
"HTEnCounter2 $HTEnCounter2"
"JSONEnCounter $JSONEnCounter"