NullInjectorError: No provider for MatDialogRef

I had this error when adding dialogs to a service to be shared in many components. Just to clarify, the error wasn’t present in the application before moving dialogs to the service. The solution was to include a custom provider MatDialogRef in the main module

  import { DialogService } from './services/dialog.service';
  import { MatDialogModule, MatDialogRef } from '@angular/material/dialog';
  ...
  imports: [
    ...
    MatDialogModule
  ],
  providers: [
     {
       provide: MatDialogRef,
       useValue: {}
     },
     DialogService
  ],
  ...

With this provider the service worked as a singleton with my dialogs to be shared and the provider error was gone.