/// <summary>
/// <see cref="HttpClientHandler"/>'s GetRequestStreamCallback uses an
/// overload of EndGetRequestStream that <see cref="HttpWebRequestWrapperRecorder"/>
/// can't intercept (method isn't virtual). So we need to intercept the call
/// and force using <see cref="HttpWebRequestWrapperRecorder.EndGetRequestStream(System.IAsyncResult)"/>
/// (which is intercepted)
/// </summary>
private static void CustomGetRequestStreamCallback(IAsyncResult ar, HttpClientHandler httpClientHandler)
{
// build a wrapper around the Request State stored in AsyncState
var requestStateWrapper = new HttpClientHandlerRequestStateWrapper(ar.AsyncState);
// get the HttpRequestMessage we've intercepted
var requestMessage = requestStateWrapper.GetHttpRequestMessage();
// load the HttpWebRequest we've already intercepted and replaced
var httpWebRequest = requestStateWrapper.GetHttpWebRequest();
// get a copy of the request streams
var requestStream = httpWebRequest.EndGetRequestStream(ar);
// copy the request message content to the request stream
requestMessage.Content.CopyToAsync(requestStream).Wait();
// save the request stream to the request state
requestStateWrapper.SetRequestStream(requestStream);
// continue on with StartGettingResponse
httpClientHandler.StartGettingResponse(ar.AsyncState);
}