you need to express that you should have parameters in this route:

export const routes: RouterConfig = [
    { path: "", component: MainPage },
    { path: "details/:id", component: DetailsPage }
];

then, you can pass it that way:

this._router.navigate(["details", selectedItem.id]);

in your DetailsPage you can get the parameters as an observable with the ActivatedRoute service.

you need to express that you should have parameters in this route:

export const routes: RouterConfig = [
    { path: "", component: MainPage },
    { path: "details/:id", component: DetailsPage }
];

then, you can pass it that way:

this._router.navigate(["/details", selectedItem.id]);

in your DetailsPage you can get the parameters as an observable with the ActivatedRoute service.