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Adds support for async filters (i.e. action filters, etc.) by implementing a custom IAsyncActionInvoker.

Read the blog article about the alpha release.

How to use:

Swap out the default implementation IAsyncActionInvoker with Hydrogen.Extensions.Mvc5.Async.ControllerActionInvokerEx. There are two ways to do this:

1. Set the ActionInvoker property of a controller when it's constructed.

   public class HomeController : Controller { public HomeController() { ActionInvoker = ControllerActionInvokerEx.Instance; } }

2. Using your DI container of choice, register Hydrogen.Extensions.Mvc5.Async.ControllerActionInvokerEx as an implementation of IAsyncActionInvoker. You may register ControllerActionInvokerEx.Instance as a singleton.

For example (using Autofac):

builder.RegisterInstance(ControllerActionInvokerEx.Instance)
        .As<IAsyncActionInvoker>()
        .SingleInstance();

Creating an async filter

You may create a subclass of AsyncActionFilterAttribute or AsyncExceptionFilterAttribute and override the async methods.

For example:

public class MyAsyncActionFilterAttribute : AsyncActionFilterAttribute
{
    public override async Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next)
    {
        // Execute code before the action is invoked.
        // You can "short-circuit" the action by setting 'context.Result'
        // and returning before calling 'next()'.
        
        // The implementation is responsible for calling 'next()'.
        var actionExecutedContext = await next().ConfigureAwait(false);

        // Execute code after the action is invoked
    }

    public override async Task OnResultExecutionAsync(ResultExecutingContext context, ResultExecutionDelegate next)
    {
        // Execute code before the result is invoked.
        // You can "short-circuit" the action by setting 'context.Canceled = true'
        // and returning before calling 'next()'.
        
        // The implementation is responsible for calling 'next()'.
        var resultExecutedContext = await next().ConfigureAwait(false);

        // Execute code after the result is invoked
    }
}

Alternately you may implement any of the async filters:

• IAsyncActionFilter
• IAsyncResultFilter
• IAsyncExceptionFilter
• IAsyncAuthorizationFilter

Unfortunately, for compatibility reasons, you must also implement the non-async version of these filters (e.g. void OnActionExecuting(ActionExecutingContext filterContext)). However, these methods can be a NOOP since the code is never executed by ControllerActionInvokerEx.

This library, currently, does not implement as async version of IAuthenticationFilter.