Pass entire hashtable to Invoke-Expression - powershell

Question

I would like to ask you for an question about passing hashtable to Invoke-Expression.
Iam writing simple E2E monitoring and mentioned hashtable is used as a body containing creds for HTTP form to log jira.
It works for me fine, but from specific reason I would like to create this Invoke-Webrequest dynamically, depending on recieved arguments.
And there is my catch.
Thus, I don't know, how to pass hashtable (other data types are ok, like a string or int) to Invoke Expression.
It is always presented like System.Collections.Hashtable
$uri = 'https://exdom.com/login.jsp?saml_sso=false'
$method = "POST"
$postParams = #{
os_username = "username";
os_password = "password";
login = "true"
}
$scriptBlock = {
param(
[Parameter(Mandatory=$true,Position=1)][string]$uri,
[Parameter(Mandatory=$false,Position=2)][string]$method,
[Parameter(Mandatory=$true,Position=3)][hashtable]$postParams
)
$commandFragments = #()
$commandFragments += "Invoke-WebRequest"
if ( $PSBoundParameters.ContainsKey('uri')){
$commandFragments += " -Uri $uri"
}
if ( $PSBoundParameters.ContainsKey('method')){
$commandFragments += " -Method $method"
}
if ( $PSBoundParameters.ContainsKey('postParams')){
$commandFragments += " -Body $postParams"
}
$commandFromFragments = $commandFragments -join ''
(Invoke-Expression -Command $commandFromFragments).Content | Out-File 'c:\tmp\response3.html'
(Invoke-Expression -Command "Invoke-WebRequest -Uri https://exdom.com/login.jsp?saml_sso=false -Method POST -Body #(#{'os_username' = 'username#mydomain.com'; 'os_password' = 'mypassword'; 'login' = 'true'})").Content | Out-File 'c:\tmp\response4.html'
(Invoke-WebRequest -Method $method -Uri $uri -Body $postParams).Content | Out-File 'c:\tmp\response5.html'
}
Invoke-Command -ScriptBlock $scriptBlock -ArgumentList ($uri, $method, $postParams)
Iam missing something basic, I guess.
May I ask you for an advice?
Thanks, Marcel

Answer 1

Lets talk about whats wrong.
$commandFragments += " -Body $postParams"
You are turning a HashTable into a string. Which is not possible. So what we can do is convert it into something. Now what should we convert into? Invoke-WebRequest -body
This can be done with Json. So you could use " -Body $($postParams | convertto-json)"
But this is only saving the json to a string which still wouldnt work because the Json needs to be in a string inside the command Invoke-WebRequest. So the fix would be to surround the JSON with single quotes. " -Body '$($postParams | ConvertTo-Json)'"
We also have some small fixes we can do for efficiency. Like the if statements looking
$PSBoundParameters.GetEnumerator() | %{
switch($_.Key){
"uri" { $commandFragments += " -Uri $uri" }
"method" { $commandFragments += " -Method $method" }
"postParams" { $commandFragments += " -Body '$($postParams | ConvertTo-Json)'" }
}
}
The final product being
$uri = 'https://exdom.com/login.jsp?saml_sso=false'
$method = "POST"
$postParams = #{
"os_username" = "username";
"os_password" = "password";
"login" = "true"
}
$scriptBlock = {
param(
[Parameter(Mandatory=$true,Position=1)][string]$uri,
[Parameter(Mandatory=$false,Position=2)][string]$method,
[Parameter(Mandatory=$true,Position=3)][hashtable]$postParams
)
$commandFragments = $("Invoke-WebRequest")
$PSBoundParameters.GetEnumerator() | %{
switch($_.Key){
"uri" { $commandFragments += " -Uri $uri" }
"method" { $commandFragments += " -Method $method" }
"postParams" { $commandFragments += " -Body '$($postParams | ConvertTo-Json)'" }
}
}
(Invoke-Expression -Command $($commandFragments -join '')).Content | Out-File 'c:\tmp\response3.html'
(Invoke-Expression -Command "Invoke-WebRequest -Uri https://exdom.com/login.jsp?saml_sso=false -Method POST -Body #(#{'os_username' = 'username#mydomain.com'; 'os_password' = 'mypassword'; 'login' = 'true'})").Content | Out-File 'c:\tmp\response4.html'
(Invoke-WebRequest -Method $method -Uri $uri -Body $postParams|ConvertTo-Json).Content
}
Invoke-Command -ScriptBlock $scriptBlock -ArgumentList ($uri, $method, $postParams)