dashboard.component.ts

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

@Component({
  selector: 'app-dashboard',
  templateUrl: './dashboard.component.html',
  styleUrls: [ './dashboard.component.css' ]
})

Changed to:

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

@Component({
  selector: 'app-dashboard',
  templateUrl: './dashboard.component.html',
  styleUrls: [ './dashboard.component.css' ]
})
export class DashboardComponent {
}

---------------UPDATE----------

你的DashboardComponent沒有導(dǎo)出任何東西啊

export class DashboardComponent implements OnInit {

    //some code

只需要改動App.module.ts中的內(nèi)容，如下：

@NgModule({
  declarations: [
    AppComponent,
    DashboardComponent
  ],
  imports: [
    BrowserModule,
    AppRoutingModule
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

強(qiáng)調(diào)一點(diǎn)，Component在declarations中的，Module在import中的，這樣你就不會出錯了。