Custom route constraint

RouteConstraintExample.cs

    public class PageRouteConstraint : IRouteConstraint
    {
        private static readonly Regex regex = new Regex($"^page=(\\d+)$");
        
        public bool Match(HttpContext httpContext, IRouter route, string routeKey, RouteValueDictionary values, RouteDirection routeDirection)
        {
            if (routeDirection != RouteDirection.IncomingRequest || !values.TryGetValue(routeKey, out var page))
            {
                return false;
            }

            var segment = page.ToString();
            var match = regex.Match(segment);
            if (match.Success)
            {
                values[routeKey] = match.Groups[1];
            }
            return true;

        }
    }
    
// ConfigureServices
services.AddRouting(x =>
{
    x.ConstraintMap.Add("page", typeof(PageRouteConstraint));
});

// Configure
app.UseMvc(routes =>
{
    routes.MapRoute("myRoute", "{controller}/{action}/{page:page?}/");
});