Cannot bind argument to parameter 'InputObject' because it is null - powershell

Question

I have a powershell script that measures download time on some pages, however I get the error above, I am unsure what I am doing wrong
error is
Cannot bind argument to parameter 'InputObject' because it is null.
function ResponseTime($CommonName,$URL, $environment)
{
$Times = 5
$i = 0
$TotalResponseTime = 0
Write-HOst $URL
While ($i -lt $Times) {
$Request = New-Object System.Net.WebClient
$Request.UseDefaultCredentials = $true
$Start = Get-Date
Write-HOst $URL
$PageRequest = $Request.DownloadString($URL)
$TimeTaken = ((Get-Date) - $Start).TotalMilliseconds
$Request.Dispose()
$i ++
$TotalResponseTime += $TimeTaken
}
$AverageResponseTime = $TotalResponseTime / $i
Write-Host Request to $CommonName took $AverageResponseTime ms in average -ForegroundColor Green
$details = #{
Date = get-date
AverageResponseTime = $AverageResponseTime
ResponseTime = $Destination
Environment = $environment
}
$results += New-Object PSObject -Property $details
$random = Get-Random -minimum 1 -maximum 30
Start-Sleep -s $random
}
#PRODUCTION
ResponseTime -commonname 'app homepage' -URL 'https://url1' -environment 'PRODUCTION'
ResponseTime -commonname 'department homepage' -URL 'https://url2' -environment 'PRODUCTION'
$results | export-csv -Path c:\so.csv -NoTypeInformation

Answer 1

Reviewing your last edit, it seems that $results simply returns $null (As your error says)
The only line setting $results is $results += New-Object PSObject -Property $details
It is not in the scope of your Export-CSV call and - even if it would, $results could be empty, if this line is not called.
You should IMHO set it to e.g. an ArrayList like follows:
$results = New-Object -TypeName System.Collections.ArrayList
And add items to it via
$times = ResponseTime -commonname '' #etc
$results.Add($times) | Out-Null
This gives you an ArrayList - even if there are no items in it - which can easily be transformed to CSV and other formats.

Answer 2

#Clijsters has given the correct answer; i.e. the issue being the scope of your $results variable.
This answer just provides a bit of a code review to help you with other bits going forwards...
function Get-ResponseTime {
[CmdletBinding()]
param (
[Parameter(Mandatory = $true)]
[string]$CommonName
,
[Parameter(Mandatory = $true)]
[string]$URL
,
[Parameter(Mandatory = $true)]
[string]$Environment
,
[Parameter(Mandatory = $false)]
[int]$Times = 5
)
[System.Int64]$TotalResponseTime = 0
[System.Diagnostics.Stopwatch]$stopwatch = New-Object 'System.Diagnostics.Stopwatch'
Write-Verbose "Processing URL: $URL"
1..$times | foreach-object {
[System.Net.WebClient]$Request = New-Object 'System.Net.WebClient'
$Request.UseDefaultCredentials = $true
Write-Verboset "Call $_ to URL: $URL"
$stopwatch.Restart()
$PageRequest = $Request.DownloadString($URL)
$stopwatch.Stop()
$TimeTaken = $stopwatch.Elapsed.TotalMilliseconds
$Request.Dispose()
$TotalResponseTime += $TimeTaken
}
$AverageResponseTime = $TotalResponseTime / $Times
Write-Verbose "Request to $CommonName took $AverageResponseTime ms on average"
$details = #{
Date = get-date
AverageResponseTime = $AverageResponseTime
#ResponseTime = $Destination #this is not declared anywhere / don't know what this field's for
Environment = $environment
}
Write-Output (New-Object 'PSObject' -Property $details)
#do you really want a delay here? Doesn't make much sense... may make sense to include a delay in the above loop; i.e. to stagger your tests?
#$random = Get-Random -minimum 1 -maximum 30
#Start-Sleep -s $random
}
#PRODUCTION
[PSObject[]]$results = #(
(Get-ResponseTime -commonname 'app homepage' -URL 'https://url1' -environment 'PRODUCTION' -Verbose)
,(Get-ResponseTime -commonname 'department homepage' -URL 'https://url2' -environment 'PRODUCTION' -Verbose)
)
$results | Export-Csv -LiteralPath 'c:\so.csv' -NoTypeInformation
Use verb-noun function names (e.g. Get-Item). What is the naming convention for Powershell functions with regard to upper/lower case usage?
Use "Cmdlets" (Advanced Functions) instead of (Basic) Functions; they're basically the same thing, only tagged with [Cmdletbinding()]. The reason for this you get support for functionality such as verbose output. http://www.lazywinadmin.com/2015/03/standard-and-advanced-powershell.html
Use a stopwatch to time processes (you could also use measure-command; but any output would be suppressed / consumed by the measure-command function). Timing a command's execution in PowerShell
Have your cmdlet output its values to the pipeline via Write-Output (or you can leave off the function name; any output caused by placing a variable with nothing to process it will be fed to the pipeline; i.e. write-object $a is the same as a line solely consisting of $a).
Capture the output into your $results variable outside of the function, and handle the results there.