Catch-all route with IRouteConstraint in ASP.Net Core 3

Question

I'm using .Net Core MVC 3.0 which defaults to Endpoint Routing

The default route config is:

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllerRoute(
                name: "default",
                pattern: "{controller=Link}/{action=Index}/{id?}"
        });

That will allow me to do CRUD operations on my "Links"
e.g. /Link/Edit/123

What I need to be able to do is catch and route any request which is NOT a CRUD operation to another controller and action
e.g. /blahblah
So that I can process them as I like (probably a redirect, maybe just a friendly notice, could be anything!)

Back in my .Net Framework MVC, one would add a route config like this:

        routes.MapRoute(
            name: "MyCatchAll",
            url: "{key}",
            defaults: new { controller = "MyController", action = "MyAction" },
            constraints: new { key = new MyConstraint() }
        );

(the purpose of the constraint is simply an optional check that I might need to use for example, to ensure that blahblah matches an expected value)

However, I cannot get this to work in .Net Core MVC 3.0

Any pointers would be most appreciated.

Answer 1

For asp.net core 3.0, you could use below configuration:

app.UseEndpoints(endpoints =>
{
    endpoints.MapControllerRoute(
        name: "MyCatchAll",
        pattern: "{key}",
        defaults: new { controller = "MyController", action = "MyAction" },
        constraints: new { key = new MyConstraint() }
    );
    endpoints.MapControllerRoute(
        name: "default",
        pattern: "{controller=Home}/{action=Index}/{id?}");
    endpoints.MapRazorPages();
});

MyConstraint.cs

public class MyConstraint: IRouteConstraint
{
    public bool Match(HttpContext httpContext,
                        IRouter router,
                        string parameterName,
                        RouteValueDictionary values,
                        RouteDirection routeDirection)
    {
        var url = values["key"];
        //your logic to check
        return true;
    }
}