Can't turn curl into Invoke-WebRequest - powershell

Question

I've got a curl command that works great and I'm trying to turn it into a PowerShell Invoke-WebRequest call.
Here's the working curl with the multipart POST data:
curl -X POST "http://domain.com/admin/batchOrder/processBatch"
-F "ordersFile=#c:\temp\Sample_Auto_Order_Input_File.xml"
-F "psid=3002010250764"
-F "recipients[0]=astraljack#example.com"
And here's where I'm trying to do it via Invoke-WebRequest. Based on what I've read, I need to create a hash table of name-value pairs. I feel like I should be creating the hash table just like I do the multipart POST data above.
$form.clear()
$form.Add("ordersFile", "c:\temp\Sample_Auto_Order_Input_File.xml")
$form.Add("psid", "3002010250764")
$form.Add("recipients[0]", "astraljack#example.com")
$form
Then I can call Invoke-WebRequest.
Invoke-WebRequest http://domain.com/admin/batchOrder/processBatch -Body $form -Method Post
This fails with a 400 Bad Request. To be clear, I've never gotten this Invoke-WebRequest to work so I could be way off base here. I'm not even sure where I can look for a better error msg.
If it helps, the contents of the exception are
IsMutuallyAuthenticated : False
Cookies : {}
Headers : {Connection, Transfer-Encoding, Content-Type, Date...}
SupportsHeaders : True
ContentLength : -1
ContentEncoding :
ContentType : application/json;charset=UTF-8
CharacterSet : UTF-8
Server : Apache
LastModified : 5/12/2014 10:23:19 AM
StatusCode : BadRequest
StatusDescription : Bad Request
ProtocolVersion : 1.1
ResponseUri : http://domain.com/admin/batchOrder/processBatch
Method : POST
IsFromCache : False

Answer 1

The best way to solve the problem is to go download Fiddler and then capture the CURL request. Inspect its RAW request. Then do the same for the Invoke-WebRequest command. See what is different and that should tell you what you need to tweak with Invoke-WebRequest.

Answer 2

The #filepath syntax in curl actually reads the contents of the file into the parameter, but in your PowerShell version you are just setting the value of ordersFile to the filename. Try:
$form.clear()
$form.Add("ordersFile", (get-content "c:\temp\Sample_Auto_Order_Input_File.xml"))
$form.Add("psid", "3002010250764")
$form.Add("recipients[0]", "astraljack#example.com")
$form
Also, you may need to add -ContentType "application/x-www-form-urlencoded" to your Invoke-WebRequest call.
`

Answer 3

I know this is an old question, but I figured since it was still unanswered, I'd throw in my two cents. Here's how I would do this:
$form = #{
'ordersFile' = 'c:\temp\Sample_Auto_Order_Input_File.xml'
'psid' = '3002010250764'
'recipients[0]' = 'astraljack#example.com'
}
Invoke-WebRequest -Uri "http://domain.com/admin/batchOrder/processBatch" -Body $form -Method Post