Added workaround for Additional fragment marker being added under .NET Framework when redirect url contains fragment

Author: TalAloni

StandardSocketsHttpHandler.FunctionalTests/HttpClientHandlerTest.cs

@@ -1082,12 +1082,6 @@ public async Task GetAsync_AllowAutoRedirectTrue_RetainsOriginalFragmentIfApprop
                 return;
             }
 
-            if (IsNetfxHandler)
-            {
-                // Similarly, netfx doesn't send fragments at all.
-                return;
-            }
-
             if (IsWinHttpHandler)
             {
                 // According to https://tools.ietf.org/html/rfc7231#section-7.1.2,
@@ -1108,6 +1102,24 @@ public async Task GetAsync_AllowAutoRedirectTrue_RetainsOriginalFragmentIfApprop
             {
                 await LoopbackServer.CreateServerAsync(async (origServer, origUrl) =>
                 {
+#if NET472
+                    // .NET Framework 4.7.2 / 4.8 UriBuilder will always append the fragment marker ('#') to fragment starting with '#',
+                    // while .NET Core will only append the fragment marker if not already present.
+                    if (origFragment.StartsWith("#"))
+                    {
+                        origFragment = origFragment.Substring(1);
+                    }
+
+                    if (redirFragment.StartsWith("#"))
+                    {
+                        redirFragment = redirFragment.Substring(1);
+                    }
+
+                    if (expectedFragment.StartsWith("#"))
+                    {
+                        expectedFragment = expectedFragment.Substring(1);
+                    }
+#endif
                     origUrl = new UriBuilder(origUrl) { Fragment = origFragment }.Uri;
                     Uri redirectUrl = new UriBuilder(origUrl) { Fragment = redirFragment }.Uri;
                     if (useRelativeRedirect)

StandardSocketsHttpHandler/Net/Http/SocketsHttpHandler/RedirectHandler.cs

@@ -108,6 +108,14 @@ private Uri GetUriForRedirect(Uri requestUri, HttpResponseMessage response)
                 string redirectFragment = location.Fragment;
                 if (string.IsNullOrEmpty(redirectFragment))
                 {
+#if NETSTANDARD20
+                    // .NET Framework 4.7.2 / 4.8 UriBuilder will always append the fragment marker ('#') to fragment starting with '#',
+                    // while .NET Core will only append the fragment marker if not already present.
+                    if (requestFragment.StartsWith("#"))
+                    {
+                        requestFragment = requestFragment.Substring(1);
+                    }
+#endif
                     location = new UriBuilder(location) { Fragment = requestFragment }.Uri;
                 }
             }