I'm getting "Property 'router' does not exist on type 'SigninComponent'." while using this.router.navigate(['/dashboard']); in angular 4

You need to pass it inside the constructor as follows,

constructor(private router: Router){
}

Also make sure you have imported Router as follows

import { Router } from '@angular/router';

/* Missing if you are using 'this.router.navigate' */   

import { Router } from '@angular/router';