CoreWebView2.NavigateToString(String) method fails to load an HTML page

Question

CoreWebView2.NavigateToString(String) method fails to load an HTML page

AdiGeo 20

I am using an instance of WebView2 class to display some HTML content in a UI panel for a VS 2022 extension. I can retrieve the HTML content that I want to display in the WebView2 control as a string, and then I am trying to use myWebView2.CoreWebView2.NavigateToString(myHTMLPage) method to have the retrieved page displayed. The HTML content has a lot of JavaScript code in it, and while loading I am getting the following exception:

Uncaught DOMException: Failed to read the 'sessionStorage' property from 'Window': Access is denied for this document.

The JavaScript code needs to access the Window.sessionStorage, but I found that the value is undefined.

As a workaround, I save the HTML content in a temporary HTML file in the file system, and I use myWebView2.CoreWebView2.Navigate(myHTMLfile). This time the page loads and displays successfully. I delete the file once the page has loaded.

I wonder if when using the NavigateToString() method is there any solution to successfully display the page? I want to avoid creating a temporary file.

Thank you

Accepted answer

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Answer 1

If the WebView is initialized, the next experimental button handler shows the usage of WebResourceRequested event, which allows to deliver the local contents:

private void button1_Click( object sender, EventArgs e )
{
    webView.CoreWebView2.AddWebResourceRequestedFilter( "file://demo/*", CoreWebView2WebResourceContext.All );

    webView.CoreWebView2.WebResourceRequested += ( s, a ) =>
    {
        if( a.Request.Uri == "file://demo/test1.html" )
        {
            string html = @"<html>
<head>
<script>
function OnLoad()
{
   try 
   {                        
      alert( window.sessionStorage);
      alert( window.sessionStorage.getItem('myKey') );
      window.sessionStorage.setItem('myKey', Date.now() );
   } 
   catch(error) 
   {
      alert(error);
   }
}
</script>
</head>
<body onload=""OnLoad()"">
<h1>TEST</h1>
<p>
Hello!
</p>
</body>
</html>";

            var ms = new MemoryStream( Encoding.UTF8.GetBytes( html ) );
            a.Response = webView.CoreWebView2.Environment.CreateWebResourceResponse( ms, 200, "OK", "Content-Type: text/html" );
        }
    };

    webView.CoreWebView2.Navigate( "file://demo/test1.html" );
}

Accessing the window.sessionStorage object in this sample should not fail. Maybe it will work in your tests too.

For specific details and optimizations, see:

https://learn.microsoft.com/en-us/microsoft-edge/webview2/concepts/working-with-local-content

AdiGeo 20 Reputation points

2024-11-01T15:08:24.2166667+00:00

Thank you again for this solution.

Answer 2

AdiGeo 20

I just tried the solution you proposed, and works perfect.

Many thanks,

Jeanine Zhang-MSFT 11,356 Reputation points Microsoft External Staff

2024-11-01T01:16:42.0166667+00:00

I am glad you have got your solution and if your case has been solved, please help to mark the answer.

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CoreWebView2.NavigateToString(String) method fails to load an HTML page

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