update/create TFS Server variable group using REST API with powershell gives object reference not set - rest

Question

Allright i have been fiddling with this for a few hours now and i can't seem to find any resources online or solve the issue.
Looking at the api documentation at https://learn.microsoft.com/en-us/rest/api/azure/devops/distributedtask/variablegroups/get?view=azure-devops-rest-6.0
I can get info regarding the variable group that i created as a test:
$invRestMethParams = #{
Uri = "https://xxx.xxx.nl/tfs/DefaultCollection/$($project)/_apis/distributedtask/variablegroups/242/?api-version=6.0-preview.2"
Method = 'GET'
ContentType = 'application/json'
}
Invoke-RestMethod #invRestMethParams -UseDefaultCredentials
I then convert the result to json to get the required values for the PUT or POST to update or create:
{
"variables": {
"check": {
"value": "value"
}
},
"id": 242,
"type": "Vsts",
"name": "TestUpdate",
"description": "",
"isShared": false,
"variableGroupProjectReferences": [
{
"projectReference": "#{id=0add8cd8-0fc8-4aca-8eb4-164cd8d09c9d; name=AutoUpdateVariableGroups}",
"name": "TestUpdate",
"description": ""
}
]
}
The documentation states the update url is:
PUT https://{instance}/{collection}/_apis/distributedtask/variablegroups/{groupId}?api-version=6.0-preview.2
With request body having the above json values (without the ID as this is in the URI). So my update json becomes:
$body = #"
{
"variables": {
"checkupdated": {
"value": "valueupdated"
}
},
"type": "Vsts",
"name": "TestUpdate",
"description": "",
"isShared": false,
"variableGroupProjectReferences": [
{
"projectReference": "#{id=0add8cd8-0fc8-4aca-8eb4-164cd8d09c9d; name=AutoUpdateVariableGroups}",
"name": "TestUpdate",
"description": ""
}
]
}
"#
i convert it from json to see if its valid (no errors).
and use it in my PUT request:
$invRestMethParams = #{
Uri = "https://xxx.xxx.nl/tfs/DefaultCollection/_apis/distributedtask/variablegroups/242/?&api-version=6.0-preview.2"
Method = 'PUT'
ContentType = 'application/json'
Body = $body
}
Invoke-RestMethod #invRestMethParams -UseDefaultCredentials
The error i receive is:
Invoke-RestMethod : {"$id":"1","innerException":null,"message":"Object reference not set to an instance of an object.","typeName":"System.NullReferenceException, mscorlib","typeKey":"NullReferenceException","errorCode":0,"eventId":0}
At line:32 char:1
+ Invoke-RestMethod #invRestMethParams -UseDefaultCredentials
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (System.Net.HttpWebRequest:HttpWebRequest) [Invoke-RestMethod], WebException
+ FullyQualifiedErrorId : WebCmdletWebResponseException,Microsoft.PowerShell.Commands.InvokeRestMethodCommand
Not sure how to troubleshoot this, does anyone know how to fix this issue? seems i am forgetting a value but im kinda lost as to what is the issue here.

Answer 1

From your script, it seems that it has issue with your request body.
In projectReference field, you need to use , to replace the ; and you need to modify the format.
"projectReference": {"id":"projectID", "name":"projectname"},
Refer to my sample:
$JSON = #"
{
"variables": {
"checkupdate": {
"value": "vaslueupdate"
}
},
"type": "Vsts",
"name": "AA",
"description": "",
"isShared": false,
"variableGroupProjectReferences": [
{
"projectReference": {"id":"108e4d7c-0bf3-4940-80da-4793f83def92", "name":"kevin1012"},
"name": "AA",
"description": ""
}
]
}
"#