选择DropDown值，然后使用Angular 6导航到页面

// app.component.html
<select [(ngModel)]="selectedValue">
  <option value="page1">Page 1</option>
  <option value="page2">Page 2</option>
  <option value="page3">Page 3</option>
</select>
<button (click)="navigateToPage()">Go</button>

// app.component.ts
import { Component } from '@angular/core';
import { Router } from '@angular/router';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  selectedValue: string;

  constructor(private router: Router) {}

  navigateToPage() {
    switch (this.selectedValue) {
      case 'page1':
        this.router.navigate(['/page1']);
        break;
      case 'page2':
        this.router.navigate(['/page2']);
        break;
      case 'page3':
        this.router.navigate(['/page3']);
        break;
      default:
        break;
    }
  }
}

// app.module.ts
import { NgModule } from '@angular/core';
import { RouterModule, Routes } from '@angular/router';
import { AppComponent } from './app.component';
import { Page1Component } from './page1.component';
import { Page2Component } from './page2.component';
import { Page3Component } from './page3.component';

const routes: Routes = [
  { path: 'page1', component: Page1Component },
  { path: 'page2', component: Page2Component },
  { path: 'page3', component: Page3Component }
];

@NgModule({
  declarations: [
    AppComponent,
    Page1Component,
    Page2Component,
    Page3Component
  ],
  imports: [
    RouterModule.forRoot(routes)
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }