public static class MyTagHelpers
    {
        public static string Prepare(this IUrlHelper helper, string value)
        {
            if (helper == null)
                throw new ArgumentNullException(nameof(helper));

            if (value.EndsWith("Controller"))
                return value[..^10];
            if (value.EndsWith("Async"))
                return value[..^5];
            return value;
        }
    }


    <form method="post"
          asp-controller="@Url.Prepare(nameof(FooController))"
          asp-action="@Url.Prepare(nameof(FooController.BarsAsync))"></form>