ActionFilterAttribute: When to use OnActionExecuting vs. OnActionExecutingAsync?

Question

I made a LoggedAttribute class that inherited from System.Web.Http.Filters.ActionFilterAttribute and put logging into OnActionExecuting and OnActionExecutingAsync methods; I had assumed one would be used for async calls and one would be used for non-async calls, but it seems both are being used. So which one should I put my logging in?

UPDATE

Code follows:

public sealed class LoggedAttribute : ActionFilterAttribute
{
    private readonly ILog _logger;

    public LoggedAttribute(ILogManager logManager)
    {
        _logger = logManager.GetLogger<LoggedAttribute>();
    }

    public LoggedAttribute() : this(new LogManager()) {}

    public override void OnActionExecuting(HttpActionContext actionContext)
    {
        //logging logic goes here
        base.OnActionExecuting(actionContext);
    }

    public override async Task OnActionExecutingAsync(HttpActionContext actionContext, CancellationToken cancellationToken)
    {
        //logging logic goes here
        await base.OnActionExecutingAsync(actionContext, cancellationToken);
    }
}

I then apply the [Logged] attribute to my base ApiController, and I am getting duplicate log entries for single calls.

Answer 1

The reply doesn't answer the question I think,

Both are used if you need to run your code before executing the action.

If you want it also to be ran SYNCHRONOUSLY use OnActionExecuting, otherwise use OnActionExecutingAsync (e.i. Async).