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-api-id -api-type
M:Windows.UI.Xaml.Controls.WebView.AddWebAllowedObject(System.String,System.Object)
winrt method

Windows.UI.Xaml.Controls.WebView.AddWebAllowedObject

-description

Adds a native Windows Runtime object as a global parameter to the top level document inside of a WebView.

-parameters

-param name

The name of the object to expose to the document in the WebView.

-param pObject

The object to expose to the document in the WebView.

-remarks

Use this method to expose a native Windows Runtime object as a global parameter in the context of the top level document inside of a WebView. For a Windows Runtime object to be projected, it must agile and be decorated with the AllowForWeb attribute.

Note

Runtime classes created using Microsoft Visual Basic, C# or Visual C++ component extensions (C++/CX) are agile by default. For more info, see Threading and Marshaling and Using Windows Runtime objects in a multithreaded environment.

The object passed into AddWebAllowedObject 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 does not work.

You must call AddWebAllowedObject every time WebView is navigated to a new page that accesses the native object. You can use the WebView.NavigationStarting event to inject the object when navigation begins.

-examples

This example shows how to decorate a class with the AllowForWeb attribute.

using Windows.Foundation.Metadata;

namespace MyRuntimeComponent
{
    [AllowForWeb]
    public sealed class MyNativeClass
    {
        public void NativeMethod()
        {
            ...
        }
 
        ...
    }
}

This example demonstrates using the NavigationStarting event to inject an object when navigation begins.

<WebView x:Name="webView" Source="https://www.contoso.com/index.html"
         NavigationStarting="webView_NavigationStarting"/>

private void webView_NavigationStarting(WebView sender, WebViewNavigationStartingEventArgs args) 
{ 
    if (args.Uri.Host == "www.contoso.com")  
    { 
        webView.AddWebAllowedObject("nativeObject", new MyNativeClass()); 
    } 
}

Here's how to access the native object in a script in the web page.

<script type='text/javascript'>
    nativeObject.nativeMethod(); // Call the projected WinRT method.
</script>

-see-also