How can I make an IActionFilter available to razor pages?

Question

I have this filter:

public class ViewBagFilter : IActionFilter
{
    private readonly ApplicationDbContext db;

    public ViewBagFilter(ApplicationDbContext _dbContext)
    {
        db = _dbContext;
    }

    public void OnActionExecuting(ActionExecutingContext context)
    {
        var controller = context.Controller as Controller;
        var dataFromDb = {db-query};
        controller.ViewBag.Example = dataFromDb;
    }

    public void OnActionExecuted(ActionExecutedContext context)
    {
        // do something after the action executes
    }
}

... that I am including in Startup.cs like this:

services.AddMvc(options =>
{
    options.Filters.Add(typeof(ViewBagFilter));
});

But when I navigate to any of the Identity razor pages, ViewBag.Example does not exist.

How can I make it available to razor pages as well?

This doesn't work:

services.AddRazorPages(options =>
{
    options.Filters.Add(typeof(ViewBagFilter));
});

Answer 1

Filters in Razor Pages are different to MVC. You will need to create a Razor Pages version: https://www.learnrazorpages.com/razor-pages/filters

Note that the dynamic ViewBag type is not available in the Razor Pages PageModel type.