ASP .NET Webhook Receiver
If you're really using Web API (and not MVC), your controller should be a subclass of ApiController (not Controller).
Update: So, you really don't need to handle the deserializing of JSON yourself. Web API will do that for you. Your "request" parameter shouldn't be of type "string", it should actually be of the type that you're trying to deserialize to
[HttpPost]public void PostObject([FromBody]testobject request){ // Your request object should be deserialized already.}
Take out the API in your URL and try http://localhost:xxxx/Postman. Your controller PostmanController is not a Web API (derived from Controller not ApiController class) so routing template of /api/{controller}/{id} is not correct in this case.