Please add a @Pipe/@Directive/@Component annotation. Error

You get this error when you wrongly add shared service to "declaration" in your appmodules instead of adding it to "provider".

If you are exporting another class in that module, make sure that it is not in between @Component and your ClassComponent. For example:

@Component({ ... })

export class ExampleClass{}

export class ComponentClass{}  --> this will give this error.

FIX:

export class ExampleClass{}

@Component ({ ... })

export class ComponentClass{}

Not a solution to the concrete example above, but there may be many reasons why you get this error message. I got it when I accidentally added a shared module to the module declarations list and not to imports.

In app.module.ts:

import { SharedModule } from './modules/shared/shared.module';

@NgModule({
  declarations: [
     // Should not have been added here...
  ],
  imports: [
     SharedModule
  ],

You have a typo in the import in your LoginComponent's file

import { Component } from '@angular/Core';

It's lowercase c, not uppercase

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