UWP WebView Javascript "Object doesn't support property or method"

Question

I need JavaScript in a UWP (Windows 10) WebView to call a C# method. I followed the instruction on how to use AddWebAllowedObject, but when JavaScript calls the C# function, I get this javascript error:

0x800a01b6 - JavaScript runtime error: Object doesn't support property or method 'getAppVersion'

As you see in javascript, "window.SCObject" is a valid object, but "window.SCObject.getAppVersion()" throws an error! Any idea why?

Here's my code C# code:

namespace Test
{
    [AllowForWeb]
    public sealed class HtmlCommunicator
    {
        public string getAppVersion()
        {
            PackageVersion version = Package.Current.Id.Version;
            return String.Format("{0}.{1}.{2}.{3}",
                                 version.Major, version.Minor, version.Build, version.Revision);
        }
    }


    public sealed partial class MainPage : Page
    {
        public MainPage()
        {
            this.InitializeComponent();
            this.HtmlWebView.Navigate(new Uri("ms-appx-web:///Assets/HTMLPage1.html"));
        }

        private HtmlCommunicator communicationWinRT = new HtmlCommunicator();
        private void HtmlWebView_NavigationStarting(WebView sender, WebViewNavigationStartingEventArgs args)
        {
            this.HtmlWebView.AddWebAllowedObject("SCObject", communicationWinRT);
        }
    }
}

Here's my XAML:

<Page
x:Class="Test.MainPage"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:local="using:Test"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d">

<Grid Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
    <WebView NavigationStarting="HtmlWebView_NavigationStarting" x:Name="HtmlWebView" />
</Grid>

Here's my Javascript:

<script type="text/javascript">
    function HtmlGetAppVersion() {
        if (window.SCObject) { //this is true
            var version = window.SCObject.getAppVersion(); //error occurs here
            console.log("Version: " + version);
        }
    }
</script>

Thank you.

Xie Steven · Accepted Answer · 2017-02-21 09:16:49Z

4

I saw that the HtmlCommunicator was defined in the same project, it would not work.

You need to create a separate windows universal windows runtime component project.

The MSDN documentation also has mentioned this point:

The object passed into AddWebAllowedObject(System.String,System.Object) must be imported from a Windows Runtime component that is separate from the app assembly. This is necessary for the AllowForWeb attribute to be property identified by the WebView security subsystem. If you use a class from your app project, AddWebAllowedObject(System.String,System.Object) does not work.

I've helped you test in a separate windows runtime component. It worked well.

answered Feb 21, 2017 at 9:16

Xie Steven

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