Powershell v5.1 Invoke-RestMethod Error Parsing Body - powershell

Question

I'm a beginner with Powershell who's trying to send a PUT request to Microsoft Azure to create an Application Insights log query. I'm able to get this working in Postman, but not in a powershell script. This is the error that I'm getting when running the script:
Invoke-RestMethod : {"code":"Unexpected character encountered while parsing value: S. Path '', line 0, position 0.","message":"Unexpected character encountered while parsing value: S. Path '', line 0, position 0.","innererror":{"diagnosticcontext":"f2843c54-dad7-49b5-92ab-e1dadd40e145","time":"2020-07-24T19:59:45.7979293Z"}}
At C:\Users\thophan\source\Update-AiLogQueries.ps1:58 char:9
+ Invoke-RestMethod -Method Put -Uri $uri -Header $header -Body ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (System.Net.HttpWebRequest:HttpWebRequest) [Invoke-RestMethod], WebException
+ FullyQualifiedErrorId : WebCmdletWebResponseException,Microsoft.PowerShell.Commands.InvokeRestMethodCommand
From looking at the Microsoft documentation, it looks like it's supposed to be able to take in a hashtable for the body, and I'm quite certain my syntax looks exactly the same as the one from the exameple, so I'm not sure what's going on. Below is an excerpt from my script:
$scope = "shared"
$header = #{
"Authorization" = "Bearer $token"
}
$uri = "https://management.azure.com/subscriptions/$subscriptionId/resourceGroups/$rgName/providers/microsoft.insights/components/$aiName/analyticsItems/item?api-version=2020-02-02-preview"
$difference = Compare-Object -ReferenceObject $localQueryList.value -DifferenceObject $response
if ($difference -ne $null)
{
$difference.ForEach(
{
$body = #{
Scope = $scope
Type = "query"
Name = $_.InputObject.Name
Content = $_.InputObject.Content
}
Invoke-RestMethod -Method Put -Uri $uri -Header $header -Body $body
})
}
UPDATE: Here is the documentation that I was looking at, as requested.
https://learn.microsoft.com/en-us/powershell/module/microsoft.powershell.utility/invoke-restmethod?view=powershell-5.1

Answer 1

The API requires that the body be a JSON string. You can do a simple conversion (using ConvertTo-Json) in your Invoke-RestMethod command and set the content type accordingly.
Invoke-RestMethod -Method Put -Uri $uri -Header $header -Body ($body | ConvertTo-Json) -ContentType 'application/json'