Forward POST request from asp.net core controller to different URL - asp.net-core

Question

I wanto to forward an incoming POST request to my asp.net core controller "as is" (including headers, body, from-data) to a different URL without using a middleware.
I found an example for doing that for asp.net: https://philsversion.com/2012/09/06/creating-a-proxy-with-apicontroller/
But this does not work for asp.net core, since the call to
return await http.SendAsync(this.Request);
in asp.net core accepts an HttpRequestMessage and the Request object is of type HttpRequest.
I also found some code, which creates a HttpRequestMessage from an HttpRequest, see: Convert Microsoft.AspNetCore.Http.HttpRequest to HttpRequestMessage
Using this code, the receiving endpoint (to which I forward to) gets the Body, but it does not get Form fields.
Checking the class HttpRequestMessage I saw that it does not contain a property for FormFields.
[Microsoft.AspNetCore.Mvc.HttpPost]
[NrgsRoute("api/redirect-v1/{key}")]
public async Task<HttpResponseMessage> Forward(
[FromUri] string key,
CancellationToken cancellationToken)
{
// the URL was shortened, we need to get the original URL to which we want to forward the POST request
var url = await _shortenUrlService.GetUrlFromToken(key, cancellationToken).ConfigureAwait(false);
using (var httpClient = new HttpClient())
{
var forwardUrl = new Uri(url);
Request.Path = new PathString(forwardUrl.PathAndQuery);
// see: https://stackoverflow.com/questions/45759417/convert-microsoft-aspnetcore-http-httprequest-to-httprequestmessage
var requestMessage = Request.ToHttpRequestMessage();
return await httpClient.SendAsync(requestMessage, cancellationToken);
// Problem: Forwards header and body but NOT form fields
}
}
Expected result would be that at my receiving endpoint I have the same
- headers
- body
- form fields
as in the original POST request.

Answer 1

I ended up doing the following:
[HttpPost]
[NrgsRoute("api/redirect-v1/{key}")]
public async Task<RedirectResult> Forward(string key, CancellationToken cancellationToken)
{
var url = await _shortenUrlService.GetUrlFromToken(key, cancellationToken).ConfigureAwait(false);
if (string.IsNullOrEmpty(url))
throw new BadRequestException($"Could not create forward URL from parameter {key}", "redirect-error");
using (var httpClient = new HttpClient())
{
var forwardUrl = new Uri(url);
Request.Path = new PathString(forwardUrl.PathAndQuery);
HttpResponseMessage responseMessage;
if (Request.HasFormContentType)
responseMessage = await ForwardFormData(key, httpClient, forwardUrl, cancellationToken);
else
responseMessage = await ForwardBody(key, httpClient, cancellationToken);
var queryParams = forwardUrl.GetQueryStringParams();
var lUlr = queryParams["lurl"];
return new RedirectResult(lUlr);
}
}
private async Task<HttpResponseMessage> ForwardFormData(string key, HttpClient httpClient, Uri forwardUrl, CancellationToken cancellationToken)
{
var formContent = new List<KeyValuePair<string, string>>();
HttpResponseMessage result;
if (Request.ContentType == "application/x-www-form-urlencoded")
{
foreach (var formKey in Request.Form.Keys)
{
var content = Request.Form[formKey].FirstOrDefault();
if (content != null)
formContent.Add(new KeyValuePair<string, string>(formKey, content));
}
var formUrlEncodedContent = new FormUrlEncodedContent(formContent);
result = await httpClient.PostAsync(forwardUrl, formUrlEncodedContent, cancellationToken);
}
else
{
var multipartFormDataContent = new MultipartFormDataContent();
foreach (var formKey in Request.Form.Keys)
{
var content = Request.Form[formKey].FirstOrDefault();
if (content != null)
multipartFormDataContent.Add(new StringContent(content), formKey);
}
result = await httpClient.PostAsync(forwardUrl, multipartFormDataContent, cancellationToken);
}
return result;
}
private async Task<HttpResponseMessage> ForwardBody(string key, HttpClient httpClient, CancellationToken cancellationToken)
{
// we do not have direct access to Content, see: https://stackoverflow.com/questions/41508664/net-core-forward-a-local-api-form-data-post-request-to-remote-api
var requestMessage = Request.ToHttpRequestMessage();
return await httpClient.SendAsync(requestMessage, cancellationToken);
}