How do I access PowerShell object values? [duplicate] - powershell

Question

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How can you use an object's property in a double-quoted string?
(5 answers)
Closed 1 year ago.
I currently have an Azure DevOps pipeline that makes a REST API call which returns an object of parameters:
#{location=eastus2; envName=sandbox; ...}
My PowerShell script looks like:
steps:
- powershell: |
$uri = "https://dev.azure.com/{org}/{proj}/_apis/build/latest/{buildId}?branchName={name}&api-version=6.0-preview.1"
$token = [System.Text.Encoding]::UTF8.GetBytes("$(System.AccessToken)" + ":")
$base64 = [System.Convert]::ToBase64String($token)
$basicAuth = [string]::Format("Basic {0}", $base64)
$headers = #{ Authorization = $basicAuth }
$result = Invoke-RestMethod -Method Get -Uri $uri -Headers $headers -ContentType application/json
$params = $result.templateParameters
Write-Host "##vso[task.setvariable variable=paramObj]$params"
- powershell: |
Write-Host $(paramObj)
In this first PS task I can use $params.location which will return eastus2. However, in the second PS task I get an error saying:
Line |
2 | Write-Host #{location=eastus2; envName=Sandbox; sqlDBAutoPauseDatabas …
| ~~~~~~~
| The term 'eastus2' is not recognized as a name of a cmdlet,
| function, script file, or executable program. Check the
| spelling of the name, or if a path was included, verify that
| the path is correct and try again.
Since my API call has an object of parameters, I'm trying to pass that parameter object to another task where I can then use those values. In the second task seen above I can't log the result, so of course trying to use dot notation, or Select-Object all results in the same error.
I was also attempting to iterate over the parameters object so I could do something like:
steps:
- powershell: |
...
$params = $result.templateParameters
foreach ($param in $params) {
Write-Host "##vso[task.setvariable variable=test]$param.Value"
}
- powershell: |
Write-Host $(location)
But I haven't been able to figure this out either as I keep getting the same error listed above. How do I access the parameter values in a second script without hardcoding it?

Answer 1

You've encountered the magic of expandable string parsing in PowerShell.
When you place a variable expression, like $param, inside an expandable string (a string literal bounded with " double quotes), PowerShell will attempt to resolve it's value for you - but nothing more than that - it's not going to attempt to evaluate member invocation, like $param.Value, for example.
So a string literal like this:
"$param.Value"
Will expand to:
"#{location=eastus2;...}.Value"
Notice that $params was evaluated and it's value substituted in the string, and the .Value-part is completely ignored.
To force PowerShell to evaluate expressions more complicated than simple variable references, use the $() subexpression operator:
Write-Host "##vso[task.setvariable variable=test]$($param.Value)"