How to specify accept header in http connector?

  • 7 February 2020
  • 2 replies

Userlevel 5
Badge +15

I have a http connector in a process flow which communicates with a .net core 3.0 web api. The API can both produce XML and JSON:

[Produces("application/xml", new string[] { "application/json" })]
public IActionResult Post()

If I do a call with no accept headers specified, this API returns the content as application/json. According to the documentation you can add headers to the HTTP connector:

[ { "Key": "Accept", "Value": "application/json" } ]


[ { "Key": "Accept", "Value": "application/xml" } ]

To specify the expected result content type, so if XML is required, the last header should be applied.

When I add this and execute the http connector it shows me the following message:

The 'Accept' header must be modified using the appropriate property or method.
Parameter name: name

With a stack trace:

The 'Accept' header must be modified using the appropriate property or method.
Parameter name: name

   at System.Net.WebHeaderCollection.ThrowOnRestrictedHeader(String headerName)
   at System.Net.WebHeaderCollection.Add(String name, String value)
   at Thinkwise.Shared.ObjectModel.ProcessAction.NoContext.HttpConnector.PerformInternal(ActiveProcessFlow activeFlow, Pending pendingProcessAction, TSFController targetController)
   at Thinkwise.Shared.ObjectModel.ProcessAction.Perform(ActiveProcessFlow activeFlow, Pending pendingProcessAction, TSFController sourceController)
   at Thinkwise.Shared.ActiveProcessFlow.executeActiveProcessAction(IProcessActionStartParameters startParameters)


I have no clue what I'm doing wrong, and it looks very familiar to these topics: (last post)


How can i make sure the accepted content type is as specified?


Best answer by Roel 10 February 2020, 10:26

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2 replies

Userlevel 4
Badge +1

Hello René,


It looks like some headers have to be added to the request in another way, e.g. Accept, Content-Type, Content-Lenght and maybe more. 


I created a User Story which we will get into in the upcoming sprint. When an update is available we will let you know.


Kind Regards,


Userlevel 4
Badge +1

Hello René,

The accept header will now no longer be added to the normal headers, for it has a separate property to set the value for this. This also counts for Content-Length and Content-Type headers.

If you are interested you can see a list of all special headers here:

We now use that method to check if the given header can be set in a normal way or should be set with a separate property.

The next GUI release which will come the 3rd of March will contain this fix.

If you have any further questions please let me know.

Kind Regards,