MinimalAPI Action filter never get executed

Question

I am working on a minimal API and I am trying to make an actionfilter for authentication works with it.

I tried to add my action filter directly on the endpoint registration likeso:

app.MapGet("/Users/{userId}", [ServiceFilter(typeof(CustomAuthorizationAttribute))] async (IMediator mediator, string userId) =>
    {
        //SomeCode
    });

I also tried with the attribute directly.

app.MapGet("/Users/{userId}", [CustomAuthorizationAttribute()] async (IMediator mediator, string userId) =>
    {
        //SomeCode
    });

At first I tried to make an extension to add it in a more elegant way and it didn't work either.

public static TBuilder AddCustomAuthorizationAttribute<TBuilder>(this TBuilder builder) where TBuilder : IEndpointConventionBuilder
{
    if (builder == null)
    {
        throw new ArgumentNullException(nameof(builder));
    }
    
    builder.Add(endpointBuilder =>
    {
        endpointBuilder.Metadata.Add(new CustomAuthorizationAttribute());
    });
    return builder;
}

There is my simple ActionFilter. I am placing my breakpoint under the onActionExecuting code to intercept when the attribute get called but it never get called.

public class CustomAuthorizationAttribute : ActionFilterAttribute, IAsyncActionFilter
{
   public override void OnActionExecuting(ActionExecutingContext context)
   {
        base.OnActionExecuting(context); //BreakPoint
   }

   public override Task OnActionExecutionAsync(ActionExecutingContext context,ActionExecutionDelegate actionExecutionDelegate)
   {
        return base.OnActionExecutionAsync(context, actionExecutionDelegate); //BreakPoint
   }
}

Answer 1

Action filters are part of ASP.NET Core MVC pipeline and are not applicable (at least at the moment of writing) to Minimal APIs.

UPD

Starting .NET 7 Minimal API's will have similar feature allowing to use AddFilter method. See also issue1 issue2, PR, and IRouteHandlerFilter interface.