NullInjectorError: No provider for AngularFirestore

Question

You should add providers: [AngularFirestore] in app.module.ts.

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

I had same issue and below is resolved.

Old Service Code:

@Injectable()

Updated working Service Code:

@Injectable({
  providedIn: 'root'
})

Open: ./src/app/app.module.ts
And import Firebase Modules at the top:

import { environment } from '../environments/environment';
import { AngularFireModule } from 'angularfire2';
import { AngularFirestoreModule } from 'angularfire2/firestore';

And VERY IMPORTANT:
Remember to update 'imports' in NgModule:

@NgModule({
  declarations: [
    AppComponent,
    OtherComponent // Add other components here
    ...
  ],
  imports: [
    BrowserModule,
    AngularFireModule.initializeApp(environment.firebase, 'your-APP-name-here'),
    AngularFirestoreModule
  ],
  ...
})

Give it a try, it shall now work.
For detailed information follow the angularfire2 documentation:
https://github.com/angular/angularfire2/blob/master/docs/install-and-setup.md
Good luck!

Weird thing for me was that I had the provider:[], but the HTML tag that uses the provider was what was causing the error. I'm referring to the red box below:

It turns out I had two classes in different components with the same "employee-list.component.ts" filename and so the project compiled fine, but the references were all messed up.

Adding AngularFirestoreModule.enablePersistence() in import section resolved my issue:

imports: [
    BrowserModule, AngularFireModule, 
    AngularFireModule.initializeApp(config),
    AngularFirestoreModule.enablePersistence()
]

I solved this problem by just removing firestore from:

import { AngularFirestore } from '@angular/fire/firestore/firestore';

in my component.ts file. as use only:

import { AngularFirestore } from '@angular/fire/firestore';

this can be also your problem.