Posting HTTP form without using 'Invoke-WebRequest'

Here is the code I use to post my Web requests, this is not the exact answer, but I suppose you can adapt it :

Add-Type -AssemblyName System.ServiceModel.Web, System.Runtime.Serialization, System.Web.Extensions$utf8 = [System.Text.Encoding]::UTF8function Request-Rest{  [CmdletBinding()]  PARAM (         [Parameter(Mandatory=$true)]         [String] $URL,         [Parameter(Mandatory=$false)]         [System.Net.NetworkCredential] $credentials,         [Parameter(Mandatory=$true)]         [String] $JSON)  # Remove NewLine from json  $JSON = $JSON -replace "$([Environment]::NewLine) *",""    # Create a URL instance since the HttpWebRequest.Create Method will escape the URL by default.     # $URL = Fix-Url $Url  $URI = New-Object System.Uri($URL,$true)     try  {    # Create a request object using the URI       $request = [System.Net.HttpWebRequest]::Create($URI)       # Build up a nice User Agent       $UserAgent = "Your user agent name"    $request.UserAgent = $("{0} (PowerShell {1}; .NET CLR {2}; {3})" -f $UserAgent, $(if($Host.Version){$Host.Version}else{"1.0"}),                             [Environment]::Version,                             [Environment]::OSVersion.ToString().Replace("Microsoft Windows ", "Win"))    $request.Credentials = $credentials    $request.KeepAlive = $true    $request.Pipelined = $true    $request.AllowAutoRedirect = $false    $request.Method = "POST"    $request.ContentType = "application/json"    $request.Accept = "application/json"    $utf8Bytes = [System.Text.Encoding]::UTF8.GetBytes($JSON)    $request.ContentLength = $utf8Bytes.Length    $postStream = $request.GetRequestStream()    $postStream.Write($utf8Bytes, 0, $utf8Bytes.Length)    #Write-String -stream $postStream -string $JSON    $postStream.Dispose()    try    {      #[System.Net.HttpWebResponse] $response = [System.Net.HttpWebResponse] $request.GetResponse()      $response = $request.GetResponse()    }    catch    {      $response = $Error[0].Exception.InnerException.Response;       Throw "Exception occurred in $($MyInvocation.MyCommand): `n$($_.Exception.Message)"    }    $reader = [IO.StreamReader] $response.GetResponseStream()      $output = $reader.ReadToEnd()      $reader.Close()      $response.Close()    Write-Output $output    }  catch  {    $output = @"    {      "error":1,      "error_desc":"Request-Rest Internal : Serveur access problem $($_.Exception.Message)"    }"@        Write-Output $output  }}

It looks like I was very close to getting it working. For some reason, I also needed to include __VIEWSTATE (in addition to __EVENTVALIDATION) in the POST. I was able to determine this by verifying form data via Fiddler.

$URL = "http://web.ourwebserver.com/test.aspx"$wc = new-object net.WebClient$wc.Headers.Add("Content-Type", "application/x-www-form-urlencoded")$wc.Headers.Add("User-Agent", "Mozilla/4.0 (compatible; MSIE 8.0; Windows NT 6.1; Trident/4.0; SLCC2; .NET CLR 2.0.50727)")$wc.UseDefaultCredentials = $true### EventValidation/ViewState Extraction Code ###$probe = $wc.downloadData($url)$s = [text.encoding]::ascii.getString($probe)$start = $s.indexOf('id="__VIEWSTATE"', 0) + 24$end = $s.indexOf('"', $start)$viewstate = $s.substring($start, $end-$start)$start = $s.indexOf('id="__EVENTVALIDATION"', 0) + 30$end = $s.indexOf('"', $start)$eventvalidation = $s.substring($start, $end-$start)###$NVC = New-Object System.Collections.Specialized.NameValueCollection$NVC.Add("__VIEWSTATE", $viewstate);$NVC.Add("__EVENTVALIDATION", $eventvalidation);$NVC.Add("ctl00`$MainContent`$phone", "454-454-2345");$NVC.Add("ctl00`$MainContent`$Submit", "Submit");$wc.QueryString = $NVC$Result = $WC.UploadValues($URL,"POST", $NVC)[System.Text.Encoding]::UTF8.GetString($Result)$WC.Dispose();

If you still require a reusable script, then you can leverage what I wrote for exact similar problem. I needed to post using PowerShell 2.0 only. The script is available in a nice Reusable Function here on GitHub: Request POST REST via Reusable Function