ActionFilter or RenderAction in ASP.NET MVC?

Question

I'm working on an ASP.NET MVC controller with several action methods, all of which need the same bit of data. This data requires a lookup that can only be done with the route values (so, I can't do the lookup in the constructor). I'm sure this has been discussed at length, but I've yet to find a satisfactory recommendation.

What's the best way to get this data without repeating myself in each action method? I'm working through:

• Create an Action Filter, this seems like the best bet, but where do I store the object, in the action parameters? Is it appropriate to create a ViewModel object in an action filter and pass it directly to the action methods, for them to fill out the rest of the ViewModel object?

• Create a child action (Html.RenderAction) to render this data, but this requires a second set of lookups since the child action requires another full cycle of instantiating the controller.

• Helper method/property called in each action method.

Thought or opinions on a best approach here?

Answer 1

A filter is probably your best bet and you can store the object in ViewData.

Another option (not a better one) is to create your own controller base class that overrides the ExecuteCore method and does the lookup there.

I did this for logging since I want to log each page view and I didn't want to have to add a filter to each and every controller I made. In mvc 3 there will be a way to declare global filters which can fix this as well.

Answer 2

You could override the OnActionExecuting() method in your controller and get the data there.

Answer 3

Ok, so given what you've told me, I would suggest using a custom ModelBinder.

It's the best fit for the situation. I would argue that using a filter is the wrong approach because a filter's job isn't to bind data - that's a job for a ModelBinder.

HTHs,
Charles

EDIT: I've just been thinking about it and I'm a little bit torn if you should use a model binder or not.

The general rule of thumb I just came up with is that if you need the ProjectDetails inside the action itself, use a ModelBinder but if you don't need the ProjectDetails inside the action, use an ActionFilter to just add it to your model / viewdata.

Maybe someone else could throw their 2c in.