Intercept GET requests and call custom single action in ASP.NET Core 3 Endpoints

I need to intercept GET requests in ASP.NET Core 3 and, if the request match some conditions, I need to execute an Action in a Controller (or a Page). Always the same action.

For example if the GET request match one of these:

\page1
\page2
\page3
\abc
\def

I need to execute the Controllers\CustomController.CustomAction and pass the request information to the controller Action.

I tried to create a CustomEndpointRouteBuilderExtensions following the guidance in Microsoft Docs Routing:

app.UseEndpoints(endpoints =>
{
    endpoints.MapCustom();
});

For the CustomEndpointRouteBuilderExtensions class I think I have to write a custom EndpointDataSource that contains all my dictionary of routes and the corresponding RequestDelegate that points to my CustomAction.

I followed the FrameworkEndpointDataSource sample but it uses the RequestDelegate writted directly on Startup.cs.

How can I create an Endpoint to add to the CustomDataSource?

Thanks in advance!

Update 1

I've found another way: I change the request before the UseRouting():

app.UseCustomEngine();
app.UseRouting();

public static IApplicationBuilder UseCustomEngine(this IApplicationBuilder builder)
{
    builder.Use(async (context, next) =>
    {
        if (dict.ContainsKey(context.Request.Path))
        {
            context.Request.Path = PathString.FromUriComponent("/CustomController/CustomAction");
            context.Request.QueryString = new QueryString($"?key=123");
        }
        await next.Invoke();
    });
    return builder;
}

What do you think? It's a good solution?