WPF/WinForms Blazor WebView Exception Handling

[TanayParikh]

WPF/WinForms Blazor WebView Exception Handling

Currently exceptions within Blazor code are not fatal to the underlying application, resulting in inconsistent behavior and a challenging debugging experience for developers.

Description

Updated exception handling mechanism to throw exceptions from the platform dispatch context instead of directly, so they can be consumed in WPF/WinForms applications using the standard AppDomain.CurrentDomain.UnhandledException API.

Other details

• Previously the re-thrown exception was being lost and we just saw the Unhandled Exception yellow bar within the webview. This had a serialized exception stack trace with limited additional information, making debugging the error more challenging.
• Now we're able to pass the exception along to the platform's exception handling mechanism (for WPF/WinForms)

AppDomain.CurrentDomain.UnhandledException += (sender, error) =>
{
    MessageBox.Show(text: error.ExceptionObject.ToString(), caption: "Error");
};

Helpful blogs on error handling within WPF:

• https://thecolorofcode.com/2019/08/11/how-to-show-an-unhandled-exception-window-in-wpf/
• https://blog.danskingdom.com/Catch-and-display-unhandled-exceptions-in-your-WPF-app/

Please note, this is specifically for WPF/WinForms scenarios. It's not entirely clear if there's a canonical way we can do this on MAUI yet (related discussion dotnet/maui#653).

Fixes dotnet/maui#4441

Customer Impact

Provides developers with improved insights on application errors, and increased control over exception handling. When an exception occurs, the app will crash and close, instead of remaining open in a corrupted state.

Regression?

• Yes
• No

Risk

• High
• Medium
• Low

Changes are specific to WebView for use with Blazor Hybrid. The intention of this change set is to guarantee the application DOES crash.

Verification

• Manual (required)
• Automated

Packaging changes reviewed?

• Yes
• No
• N/A

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