public delegate Task<PageHandlerExecutedContext> PageExecutionDelegate();

public class PageHandlerSelectedContext : FilterContext
{
    public virtual new CompiledPageActionDescriptor ActionDescriptor { get; }

    public virtual HandlerMethodDescriptor HandlerMethod { get; set; }

    public virtual IActionResult Result { get; set; }

    public virtual object HandlerInstance { get; }
}


public class PageHandlerExecutingContext : FilterContext
{
    public virtual new CompiledPageActionDescriptor ActionDescriptor { get; }

    public virtual HandlerMethodDescriptor HandlerMethod { get; }

    public virtual IActionResult Result { get; set; }

    public virtual IDictionary<string, object> HandlerArguments { get; }

    public virtual object HandlerInstance { get; }
}


public class PageHandlerExecutedContext : FilterContext
{
    public virtual new CompiledPageActionDescriptor ActionDescriptor { get; }

    public virtual HandlerMethodDescriptor HandlerMethod { get; }

    public virtual IActionResult Result { get; set; }

    public virtual object HandlerInstance { get; }

    public virtual bool Canceled { get; set; }

    public virtual Exception Exception { get; set; }

    public virtual ExceptionDispatchInfo ExceptionDispatchInfo { get; set; }

    public virtual bool ExceptionHandled { get; set; }
}

public interface IPageFilter : IFilterMetadata
{
    void OnPageHandlerSelected(PageHandlerSelectedContext context);

    void OnPageHandlerExecuting(PageHandlerExecutingContext context);

    void OnPageHandlerExecuted(PageHandlerExecutedContext context);
}

public interface IAsyncPageFilter : IFilterMetadata
{
    void OnPageHandlerSelection(PageHandlerSelectedContext context);

    void OnPageHandlerExecution(PageHandlerExecutingContext context, PageHandlerExecutionDelegate next);
}