什么时候覆盖ActionFilterAttribute.OnActionExecutingAsync（）？

Question

I'm implementing a custom ActionFilterAttribute and it's currently not clear whether I need to override the OnActionExecutingAsync() method. This is a project that uses ASP.NET WebAPI v5.2.3.

I've currently overridden both OnActionExecuting() and OnActionExecutingAsync() , where both methods call the same private method that does the actual work of the filter.

What I find is that both methods are getting called - first OnActionExecutingAsync() and then - from within the call to base.OnActionExecutingAsync() - OnActionExecuting() gets called.

So do I only need to override OnActionExecuting() ? If so, when would I ever need to override the async version?

Answer 1

I think you'll run into problems trying to use OnActionExecuting on an async controller because it won't be able to communicate the CancellationToken that the system uses to manage threads. You might find that OnActionExecuting fires on resumption of an action after an await , which might be a problem depending on what your filter is expecting, for example.

Based on some experimentation though, it appears that OnActionExecutingAsync works fine with non-async controllers.

Answer 2

So do I only need to override OnActionExecuting()? If so, when would I ever need to override the async version?

Only if you have a long running task in your filter.

Answer 3

Usually, when ever a method has an async version and a sync version both of them will call and you should just override or hook to one of them. For this case, you could check it in this link

    [NonAction]
    public virtual async Task OnActionExecutionAsync(
        ActionExecutingContext context,
        ActionExecutionDelegate next)
    {
        if (context == null)
        {
            throw new ArgumentNullException(nameof(context));
        }

        if (next == null)
        {
            throw new ArgumentNullException(nameof(next));
        }

        OnActionExecuting(context);
        if (context.Result == null)
        {
            OnActionExecuted(await next());
        }
    }