Last but not least, create a new /ClientApp/app/components/pagenotfound/ folder and fill it out with the following pagenotfound.component.ts file:

import { Component } from "@angular/core";

@Component({
    selector: "pagenotfound",
    templateUrl: "./pagenotfound.component.html"
})

export class PageNotFoundComponent {
    title = "Page not Found";
}

Also fill it with its corresponding pagenotfound.component.html template file:

<h2>{{title}}</h2>
<div>
    Oops... This page does not exist (yet!).
</div>

Wait a minute, aren't we forgetting something that we're require to do each and every time we add a new component? As a matter of fact, we do; we still need to add them all to the AppModule class.