Angular4.X 报错： Can't bind to 'ngModel' since it isn't a known property of 'input'

使用angular4时，应用angular指令，如ngModel时，发生如题的错误

原因： 未导入执行指令所需的文件

解决方法： 在app.module.ts文件中导入FormsModule文件，如下所示:

@NgModule({  declarations: [    AppComponent,    Product1Component,    Product2Component,    ErrorComponent  ],  imports: [    BrowserModule,    AppRoutingModule,    FormsModule  ],  providers: [    ProductService,  ],  bootstrap: [AppComponent]})export class AppModule { }