Azure DevOps how to edit Wiki page via REST API - azure-devops

Question

I want to edit a Azure DevOps wiki page over the REST API (Azure DevOps Server 2019.0.1).
When I run this PowerShell script:
#VARIABLES
$api = "api-version=5.0"
$root = "http://136.202.18.216:8070/Samples"
$personalToken = "uwawlzqp6j7i1nd5dasspwkwp63tr2w2sxb5563zrla2bivynbza"
#AUTHORIZATION
$token = [System.Convert]::ToBase64String([System.Text.Encoding]::ASCII.GetBytes(":$($personalToken)"))
$headers = #{
"Authorization" = ('Basic {0}' -f $token)
"If-Match" = '*'
}
#PROJECT VARIABLES
$project = "Framework%20A"
$pageToUpdate = "/Seite2"
#BODY
$body = #"
{
"content": "Hello"
}
"#
#GET
$url = "$root/$project/_apis/wiki/wikis/2e887fde-ce76-4180-aa8d-f26ed4799eb3/pages?version=wikiMaster&path=$pageToUpdate&includeContent=True&$api"
$content = Invoke-RestMethod -Uri $url -Method Get -ContentType "application/json" -Headers $headers
Write-Host "$($content.path) = $($content.content)" -ForegroundColor Yellow
#PUT
$url = "$root/$project/_apis/wiki/wikis/2e887fde-ce76-4180-aa8d-f26ed4799eb3/pages?version=wikiMaster&path=$pageToUpdate&$api"
$update = Invoke-RestMethod -Uri $url -Method Put -ContentType "application/json" -Headers $header -Body $body -Verbose
Write-Host $update.content -ForegroundColor Yellow
exit(0)
The consolen output is:
/Seite2 = Seite 2 Content
AUSFÜHRLICH: PUT http://136.202.18.216:8070/Samples/Framework A/_apis/wiki/wikis/2e887fde-ce76-4180-aa8d-f26ed4799eb3/pages?version=wikiMaster&path=/Seite2&api-version=5.0 with -1-byte payload
Invoke-RestMethod: {"$ id": "1", "innerException": null, "message": "The required \" IfMatch \ "header specified in the request is an invalid page version Version of the
Wiki page as \ "IfMatch \" header for the request. \ R \ nParameterName: IfMatch "," typeName ":" Microsoft.TeamFoundation.SourceControl.WebServer.InvalidArgumentValueException,
Microsoft.TeamFoundation.SourceControl.WebServer "," TypeKey ":" InvalidArgumentValueException "," error code ": 0," eventId ": 0}
In C:\Users\mkober\Desktop\Azure DevOps Skripte (Bearbeitung)\WikiAPI.ps1:34 Zeichen:11
+ $update = Invoke-RestMethod -Uri $url -Method Put -ContentType "appli ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo : InvalidOperation: (System.Net.HttpWebRequest:HttpWebRequest) [Invoke-RestMethod], WebException
+ FullyQualifiedErrorId : WebCmdletWebResponseException,Microsoft.PowerShell.Commands.InvokeRestMethodCommand
The first line /Seite2 = Seite 2 Content is the result of a successful get request from the page I want to edit. The put request occures the error. What am I doing wrong here?
UPDATE: (Working Example)
#VARIABLES
$api = "api-version=5.0"
$root = "http://136.202.18.216:8070/Samples"
$personalToken = "uwawlzqp6j7i1nd5dasspwkwp63tr2w2sxb5563zrla2bivynbza"
#AUTHORIZATION
$token = [System.Convert]::ToBase64String([System.Text.Encoding]::ASCII.GetBytes(":$($personalToken)"))
$headers = #{
"Authorization" = ('Basic {0}' -f $token)
"If-Match" = '{0}'
}
#PROJECT VARIABLES
$project = "Framework%20A"
$pageToUpdate = "/Seite2"
#BODY
$body = #"
{
"content": "Hello"
}
"#
#---------------------------------------------------------------------------------------------------------------------------
#GET
$url = "$root/$project/_apis/wiki/wikis/2e887fde-ce76-4180-aa8d-f26ed4799eb3/pages?version=wikiMaster&path=$pageToUpdate&includeContent=True&$api"
$content = Invoke-WebRequest -Uri $url -Method Get -ContentType "application/json" -Headers $headers
$etag = $content.Headers.ETag
$headers.'If-Match' = $headers.'If-Match' -f $etag
Write-Host "$($content.path) = $($content.content)" -ForegroundColor Yellow
#PUT
$url = "$root/$project/_apis/wiki/wikis/2e887fde-ce76-4180-aa8d-f26ed4799eb3/pages?version=wikiMaster&path=$pageToUpdate&$api"
$update = Invoke-RestMethod -Uri $url -Method Put -ContentType "application/json" -Headers $headers -Body $body -Verbose
Write-Host $update.content -ForegroundColor Yellow
exit(0)
#---------------------------------------------------------------------------------------------------------------------------

Answer 1

In the If-Match header you can't just put '*', you need to put there the ETag of the page.
How do you get it? in your first GET call use Invoke-WebRequest (instaed of Invoke-RestMethod), now in the response you will get also headers response and there the ETag exist:
$page = Invoke-WebRequest -Uri $url ...........
$etag = $page.Headers.ETag
$headers = #{
"Authorizaion = ....."
"If-Match" = $etag
}
Now the second Invoke-RestMethod will work to update the page.