API proposal OwningComponentBase IAsyncDisposable implementation

[javiercn]

Background and Motivation

When we implemented IAsyncDisposable in components we should probably have also added support for this on OwningComponentBase. Previously, developers faced two main problems:

When the injected service implements IAsyncDisposable, an exception is thrown: "System.InvalidOperationException: 'MyService' type only implements IAsyncDisposable. Use DisposeAsync to dispose the container."

Proposed API

namespace Microsoft.AspNetCore.Components
{
    public abstract class OwningComponentBase : ComponentBase, IDisposable, IAsyncDisposable
    {
        // ...existing members...
        
+       protected virtual ValueTask DisposeAsyncCore();
    }
}

Usage Examples

// Component with async disposable service
public class ChatComponent : OwningComponentBase<IChatService>
{
    // Service that implements IAsyncDisposable (e.g., has SignalR HubConnection)
    private IChatService ChatService => Service;
    
    protected override async ValueTask DisposeAsyncCore()
    {
        // Custom async cleanup if needed
        await base.DisposeAsyncCore();
    }
}

// Component that implements IAsyncDisposable
public class MyAsyncComponent : OwningComponentBase, IAsyncDisposable
{
    // Component's own async resources
    private SomeAsyncResource? _resource;
    
    protected override async ValueTask DisposeAsyncCore()
    {
        if (_resource != null)
        {
            await _resource.DisposeAsync();
        }
        
        await base.DisposeAsyncCore();
    }
}

Alternative Designs

The main alternative considered was to not implement this feature due to potential breaking changes. Adding IAsyncDisposable implementation with a protected virtual DisposeAsyncCore() method could clash with existing IAsyncDisposable implementations in subclasses, requiring developers to change their implementations to override the new base-class method.

Risks

1. Potential breaking changes: Existing components that inherit from OwningComponentBase and implement IAsyncDisposable may need to update their implementation to override the new DisposeAsyncCore() method instead of implementing IAsyncDisposable directly.

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