Al: How to associate an HttpHeaders collection with a WebRequest

[jcooper01]

What's the correct way to populate an HttpHeaders collection and then use it with a WebRequest? I see methods to get the headers, to get default headers, but nothing to set the headers. Also, can you set the UserAgent and Content-Type through the HttpHeaders? Some interfaces don't allow that and they need to be set through properties. We need to be able to add custom headers, set Content-Type and UserAgent, and read the headers coming back in the response.

[ajkauffmann]

Use the GetHeaders method on the HttpRequestMessage. Then on the returned object, call the Add method. No need to write back the Headers object, you don't get a copy of the headers, but a reference.

For example, Headers.Add('User-Agent','MyAgentString') should work.
For Content-Type header, you have to work with the HttpContent object. This object has also a GetHeaders method that you can call. Then call Add on the return object, like RequestHeaders.Add('Content-Type','application/x-www-form-urlencoded').

For a complete example you may want to look at this blog post: http://www.kauffmann.nl/2017/07/18/al-web-service-examples/