Running powershell script on asp.net site - asp.net

Question

I am trying to run a powershell script and have it output to my asp.net site. I have made it work with a very simple script where the only command in the script was
Get-Service | Out-String
and this output onto my site everything I expected
but when I use the script I actually want info from it doesn't output anything
I can tell it runs (or trys to run) because when my site hits the code that invokes the script it hangs about 10 seconds.
The script I am trying to run is
$user = "user"
$token = "token"
$base64AuthInfo = [Convert]::ToBase64String([Text.Encoding]::ASCII.GetBytes(("{0}:{1}" -f $user,$token)))
$result = Invoke-WebRequest -Method Get -Uri 'https://site.vsrm.visualstudio.com/defaultcollection/product/_apis/release/releases?definitionId=1&api-version=3.0-preview.2&$expand=environments' -ContentType "application/json" -Headers #{Authorization=("Basic {0}" -f $base64AuthInfo)}
$releaseArr = $result.Content | ConvertFrom-Json
[System.Collections.ArrayList]$enviromentName = #()
[System.Collections.ArrayList]$latestRelease = #()
foreach($env in $releaseArr.value[0].environments)
{
$enviromentName.Add($env.name) | Out-Null
}
foreach($releaseValue in $releaseArr.value)
{
For($i = 0; $i -lt $enviromentName.Count; $i++)
{
if($latestRelease[$i] -eq $null)
{
foreach($release in $releaseValue.environments)
{
if($release.name -eq $enviromentName[$i] -and $release.status -eq "succeeded")
{
$latestRelease.Add($releaseValue.name) | Out-Null
}
}
}
}
}
For($i = 0; $i -lt $enviromentName.Count; $i++)
{
Write-Host $enviromentName[$i] " : " $latestRelease[$i]
}
I know this script runs and outputs, but is there some code in this script that would cause it to not output properly.
The code in my asp.net site I am using to call the script is
ResultBox.Text = string.Empty;
// Initialize PowerShell engine
var shell = PowerShell.Create();
// Add the script to the PowerShell object
shell.Commands.AddScript(#"C:\Users\user\Desktop\script.ps1");
// Execute the script
var results = shell.Invoke();
// display results, with BaseObject converted to string
// Note : use |out-string for console-like output
if (results.Count > 0)
{
// We use a string builder ton create our result text
var builder = new StringBuilder();
foreach (var psObject in results)
{
// Convert the Base Object to a string and append it to the string builder.
// Add \r\n for line breaks
builder.Append(psObject.BaseObject.ToString() + "\r\n");
}
// Encode the string in HTML (prevent security issue with 'dangerous' caracters like < >
ResultBox.Text = Server.HtmlEncode(builder.ToString());
}

Answer 1

Change "Write-Host" to "Write-Output." Write-Host only outputs to interactive consoles.
You can see this in action:
Make a new PowerShell file and add a write-host statement to it:
[nick#nick-lt temp]$ New-Item -Type File -Path .\example.ps1 -Force
[nick#nick-lt temp]$ Set-Content .\example.ps1 "Write-Host 'Hello World'"
Then try and set a variable to the result of the script:
[nick#nick-lt temp]$ $what = .\example.ps1
Hello World
[nick#nick-lt temp]$ $what
[nick#nick-lt temp]$
Hello World shows up when the script executes but the variable is empty.
Now change it to write-output:
[nick#nick-lt temp]$ Set-Content .\example.ps1 "Write-Output 'Hello World'"
[nick#nick-lt temp]$ $what = .\example.ps1
[nick#nick-lt temp]$ $what
Hello World
The variable actually contains what it is supposed to now.
One of the cardinal rules of PowerShell is to not use Write-Host except in script that will be run interactively. .NET needs the results in the output stream not the host stream.