问题
I know that using HAP in windows phone apps is very problematic, but I very need to. So the problem is that when I add System.Xml.XPath from silverlight 5 or 4 I get "Xaml Internal Error error WMC9999". It's got to be noticed that the version of HAP is 1.4.6 but not 1.4.9 (tha latest one), because it cannot be installed from NuGet (just doesn't add reference) and I've found no links to download it manually. In old windows phone 8 silverlight app everything worked great. Please, help.
回答1:
Use the HtmlAgilityPack-PCL nuget package with Windows Phone 8.1 XAML apps, it works fine with no need to add any references manually.
来源：https://stackoverflow.com/questions/26698775/windows-phone-8-1-hubapp-htmlagilitypack