Like the other types of filters, the action filter can be added to different scope levels: Global, Action, and Controller. If we want to use our filter globally, we need to register it inside the AddControllers() method in the Program class:

builder.Services.AddControllers(config =>
{
    config.Filters.Add(new GlobalFilterExample());
});

But if we want to use our filter as a service type on the Action or Controller level, we need to register it, but as a service in the IoC container:

builder.Services.AddScoped<ActionFilterExample>();
builder.Services.AddScoped<ControllerFilterExample>();

Finally, to use a filter registered on the Action or Controller level, we need to place it on top of the Controller or Action as a ServiceType:

namespace AspNetCore.Controllers;

[ServiceFilter(typeof(ControllerFilterExample))]
[Route("api/[controller]")]
[ApiController]
public class TestController : ControllerBase
{
    [HttpGet]
    [ServiceFilter(typeof(ActionFilterExample))]
    public IEnumerable<string> Get()
    {
        return new string[] { "example", "data" };
    }
}

The order in which our filters are executed is as follows:

Of course, we can change the order of invocation by adding the Order property to the invocation statement:

namespace AspNetCore.Controllers;

[ServiceFilter(typeof(ControllerFilterExample), Order = 2)]
[Route("api/[controller]")]
[ApiController]
public class TestController : ControllerBase
{
    [HttpGet]
    [ServiceFilter(typeof(ActionFilterExample), Order = 1)]
    public IEnumerable<string> Get()
    {
        return new string[] { "example", "data" };
    }

}

Or something like this on top of the same action:

[HttpGet]
[ServiceFilter(typeof(ActionFilterExample), Order = 2)]
[ServiceFilter(typeof(ActionFilterExample2), Order = 1)]
public IEnumerable<string> Get()
{
    return new string[] { "example", "data" };
}

So, with all this in mind, we can start applying some action filters in our project.