import { AngularFireDatabase, FirebaseListObservable } from "angularfire2/database";

i got the answer after reading https://github.com/angular/angularfire2/blob/master/CHANGELOG.md 5.0.0-rc.0 (2017-10-03)

the -deprecated allows you to use the old database API

import { AngularFireDatabaseModule } from 'angularfire2/database-deprecated';

in the app.module.js and in your service you use

 import { AngularFireDatabase, FirebaseListObservable } from "angularfire2/database-deprecated";

thank you both of you, you helped me

You need to import the following and add it under your app.module.ts

import { AngularFireModule } from 'angularfire2';
import { AngularFireDatabaseModule } from 'angularfire2/database';


@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule,
    AngularFireModule.initializeApp(firebaseConfig),
    AngularFireDatabaseModule
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

You can't use FirebaseListObservable in current version of angularfire2.
It worked in old version of angularfire2 like 4.0.0-rc.1.

So, install it and it will work totally fine (in terminal):

npm i [email protected]

and import:

import {AngularFireDatabase,FirebaseListObservable} from 'angularfire2/database';

import { AngularFireAuthModule, AngularFireAuth } from 'angularfire2/auth';

This might be late, but in case anyone still wonders what they can use as an alternative, note that FirebaseListObservable has been deprecated.

However, in the latest version of firebase note that you can use AngularFireList, and import it as so...

import { AngularFireDatabase , AngularFireList} from '@angular/fire/database';