Order of execution with multiple filters in web api

Some things to note here:

1. Filters get executed in the following order for an action: Globally
   Defined Filters -> Controller-specific Filters -> Action-specific Filters.
2. Authorization Filters -> Action Filters -> Exception
   Filters

3. Now the problem that you seem to mention is related to
   having multiple filters of the same kind (ex: Multiple
   ActionFilterAttribute decorated on a
   controller or an action. This is the case which would not guarantee
   the order as its based on reflection.). For this case, there is a way
   to do it in Web API using custom implementation of
   System.Web.Http.Filters.IFilterProvider. I have tried the following
   and did some testing to verify it. It seems to work fine.
   You can give it a try and see if it works as you expected.

   // Start clean by replacing with filter provider for global configuration.
   // For these globally added filters we need not do any ordering as filters are 
   // executed in the order they are added to the filter collection
   config.Services.Replace(typeof(IFilterProvider), new System.Web.Http.Filters.ConfigurationFilterProvider());
   
   // Custom action filter provider which does ordering
   config.Services.Add(typeof(IFilterProvider), new OrderedFilterProvider());
   

   ---

   public class OrderedFilterProvider : IFilterProvider
   {
       public IEnumerable<FilterInfo> GetFilters(HttpConfiguration configuration, HttpActionDescriptor actionDescriptor)
       {
           // controller-specific
           IEnumerable<FilterInfo> controllerSpecificFilters = OrderFilters(actionDescriptor.ControllerDescriptor.GetFilters(), FilterScope.Controller);
   
           // action-specific
           IEnumerable<FilterInfo> actionSpecificFilters = OrderFilters(actionDescriptor.GetFilters(), FilterScope.Action);
   
           return controllerSpecificFilters.Concat(actionSpecificFilters);
       }
   
       private IEnumerable<FilterInfo> OrderFilters(IEnumerable<IFilter> filters, FilterScope scope)
       {
           return filters.OfType<IOrderedFilter>()
                           .OrderBy(filter => filter.Order)
                           .Select(instance => new FilterInfo(instance, scope));
       }
   }
   

   ---

   //NOTE: Here I am creating base attributes which you would need to inherit from.
   public interface IOrderedFilter : IFilter
   {
       int Order { get; set; }
   }
   
   public class ActionFilterWithOrderAttribute : ActionFilterAttribute, IOrderedFilter
   {
       public int Order { get; set; }
   }
   
   public class AuthorizationFilterWithOrderAttribute : AuthorizationFilterAttribute, IOrderedFilter
   {
       public int Order { get; set; }
   }
   
   public class ExceptionFilterWithOrderAttribute : ExceptionFilterAttribute, IOrderedFilter
   {
       public int Order { get; set; }
   }