Revised deletion of cookies.

src/NzbDrone.Common.Test/Http/HttpClientFixture.cs

@@ -338,6 +338,28 @@ namespace NzbDrone.Common.Test.Http
             responseCookies.Resource.Cookies.Should().BeEmpty();
         }
 
+        [Test]
+        public void should_clear_request_cookie()
+        {
+            var requestSet = new HttpRequest($"http://{_httpBinHost}/cookies");
+            requestSet.Cookies.Add("my", "cookie");
+            requestSet.AllowAutoRedirect = false;
+            requestSet.StoreRequestCookie = true;
+            requestSet.StoreResponseCookie = false;
+
+            var responseSet = Subject.Get<HttpCookieResource>(requestSet);
+
+            var requestClear = new HttpRequest($"http://{_httpBinHost}/cookies");
+            requestClear.Cookies.Add("my", null);
+            requestClear.AllowAutoRedirect = false;
+            requestClear.StoreRequestCookie = true;
+            requestClear.StoreResponseCookie = false;
+
+            var responseClear = Subject.Get<HttpCookieResource>(requestClear);
+
+            responseClear.Resource.Cookies.Should().BeEmpty();
+        }
+
         [Test]
         public void should_not_store_response_cookie()
         {

src/NzbDrone.Common/Http/HttpClient.cs

@@ -153,12 +153,23 @@ namespace NzbDrone.Common.Http
                 {
                     foreach (var pair in request.Cookies)
                     {
-                        var cookie = new Cookie(pair.Key, pair.Value, "/")
+                        Cookie cookie;
+                        if (pair.Value == null)
                         {
-                            // Use Now rather than UtcNow to work around Mono cookie expiry bug.
-                            // See https://gist.github.com/ta264/7822b1424f72e5b4c961
-                            Expires = DateTime.Now.AddHours(1)
-                        };
+                            cookie = new Cookie(pair.Key, "", "/")
+                            {
+                                Expires = DateTime.Now.AddDays(-1)
+                            };
+                        }
+                        else
+                        {
+                            cookie = new Cookie(pair.Key, pair.Value, "/")
+                            {
+                                // Use Now rather than UtcNow to work around Mono cookie expiry bug.
+                                // See https://gist.github.com/ta264/7822b1424f72e5b4c961
+                                Expires = DateTime.Now.AddHours(1)
+                            };
+                        }
 
                         sourceContainer.Add((Uri)request.Url, cookie);