Wininet seems to ignore no-cache request header.

gistfile1.cs

     private static async Task TestNoCache(string host)
        {
            var clientHandler = new WebRequestHandler();
            clientHandler.CachePolicy = new RequestCachePolicy(RequestCacheLevel.Default);
            var client = new HttpClient(clientHandler) { BaseAddress = new Uri(host) };

            var response = await client.GetAsync("/CacheableResource");

            var request = new HttpRequestMessage()
            {
                RequestUri = new Uri("/CacheableResource", UriKind.Relative)
            };

            request.Headers.CacheControl = new CacheControlHeaderValue() { NoCache = true };
            var response2 = await client.SendAsync(request);  // This should make a round-trip, but it doesn't
        
        }
        
        
    [Route("CacheableResource")]
    public class CacheableResourceController : ApiController
    {
        public HttpResponseMessage Get()
        {
            var response = new HttpResponseMessage()
            {
                Content = new StringContent("This is cached content")
            };
            response.Headers.CacheControl = new CacheControlHeaderValue() { MaxAge = new TimeSpan(0, 0, 0, 5) };
            return response;
        }

    
    }