Sample showing how to enable back navigation by clicking the "back" in a Universal app.

UniversalMouseBackButton.cs

//*********************************************************//
//    Copyright (c) Microsoft. All rights reserved.
//    
//    Apache 2.0 License
//    
//    You may obtain a copy of the License at
//    http://www.apache.org/licenses/LICENSE-2.0
//    
//    Unless required by applicable law or agreed to in writing, software 
//    distributed under the License is distributed on an "AS IS" BASIS, 
//    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or 
//    implied. See the License for the specific language governing 
//    permissions and limitations under the License.
//
//*********************************************************
namespace UniversalMouseBackButton
{
    sealed partial class App : Application
    {
        protected override void OnLaunched(LaunchActivatedEventArgs e)
        {
            //other startup code here ...
            
            Window.Current.CoreWindow.PointerReleased += (Windows.UI.Core.CoreWindow sender, Windows.UI.Core.PointerEventArgs args) => {
                if (args.CurrentPoint.Properties.PointerUpdateKind == Windows.UI.Input.PointerUpdateKind.XButton1Released)
                {
                    var frame = Window.Current.Content as Frame;
                    if (null != frame)
                    {
                        //go back
                        if (frame.CanGoBack)
                        {
                            frame.GoBack();
                        }
                    }
                }
            };
        }
    }
}