如何将参数从动作过滤器传递到控制器方法

Question

I want to make a custom authentication filter. If everything succeeds, it should return the user. But, in the controller, I need it again to find the user, but this would be inefficient to search for him once again in the database. I want to reuse the information gained in the ActionFilter . This is the pseudocode that shows exactly what I am trying to achieve:

public class AuthenticateAttribute : ActionFilterAttribute
{
    public async override void OnActionExecuting(ActionExecutingContext context)
    {
        // some code here...
        var user = // some code...

        if (user == null)
        {
            // error, not authenticated
        }

        // yes! authentication succeeded! now we have found the user, it would be clever to pass
        // it to the controller method so that it does not have to look it up once again in the database
        parameters.Add("userFound", user);
    }
}

Is there a way to do this? I would like then to access it in the controller method, no matter how. For example like this:

parameters["userFound"]

Thanks!

Answer 1

In ActionExecutingContext you have full access to controller and request then you have many places you can put your parameter, just to mention few:

• context.Controller.ViewBag , it's also accessible in your view.
• context.Controller.ViewData, it's also accessible in your view.
• context.HttpContext.Session , if you're using session.

Remember that ActionExecutingContext derives from ControllerContext and ControllerContext is accessible everywhere in your controller.

However I'd avoid this because it's (at least to me) little bit strange. Your controller will take a different action according to that parameter (not much different than a check on User.IsAuthenticated ) then what I would really do is to redirect to a differenct action method, in your action filter:

if (user == null) // not authenticated
{
    var data = context.HttpContext.Request.RequestContext.RouteData;
    var currentAction = data.GetRequiredString("action");
    var currentController = data.GetRequiredString("controller");

    context.Result = new RedirectToRouteResult(
        new RouteValueDictionary 
        { 
            { "controller", currentController }, 
            { "action", currentAction + "_NotAuthenticated" } 
    });
}