WebAssembly (Avalonia) Uncaught ManagedError: One or more errors occurred. (Cannot wait on monitors on this runtime.)

Question

I've created my browser app with AvaloniaUI, and it has next code, called from App.axaml.cs:

using (var client = new HttpClient())
{
    var task = Task.Run(() => client.GetStringAsync(_apiBaseUrl));
    task.Wait();
    var content = task.Result;
    return Deserialize<TState?>(content) ?? new();
}

This code throws PlatformNotSupportedException, when I run browser version of application:

Uncaught ManagedError: One or more errors occurred. (Cannot wait on monitors on this runtime.)

Same error occurs when I try to use .GetAwaiter().GetResult() instead of Task.Run()

Does somebody know how to make http requests from browser app?

It would be nice to have ability to reuse same code for browser and desktop version.

UPDATE:

I've tried to use sync version, because method public override void OnFrameworkInitializationCompleted() has void return type, and exception handling would be a trouble, as I know.

Answer 1

.NET on Browser (and in general for the most part) doesn't support multithreading. .NET 8 will bring some multithreading support only on the newest browser versions, but it's still going to be limited.

And you can't block the main thread in either way.

Does somebody know how to make http requests from browser app?

Use async methods without blocking.

using (var client = new HttpClient())
{
    var content = await client.GetStringAsync(_apiBaseUrl);
    return Deserialize<TState?>(content) ?? new();
}