Forms 在Angular4中，每当我添加表单标记时，ControlContainer错误没有提供程序

首先，我在app.module.ts中添加了ReactiveFormModule

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { RouterModule, Routes} from '@angular/router';
import { ReactiveFormsModule } from '@angular/forms';
import { AppComponent } from './app.component';
import { NewproducComponent } from './comp/newproduc/newproduc.component';
import { ProductsComponent } from './comp/products/products.component';
import { SidebarComponent } from './comp/sidebar/sidebar.component';
import { MenubarComponent } from './comp/menubar/menubar.component';


const appRoutes: Routes = [
  { path : '' , component : ProductsComponent},
  { path : 'newproduct' , component : NewproducComponent}
];


@NgModule({
  declarations: [
    AppComponent,
    NewproducComponent,
    ProductsComponent,
    SidebarComponent,
    MenubarComponent
  ],
  imports: [
    BrowserModule,
    ReactiveFormsModule,
    RouterModule.forRoot(appRoutes) 
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule {
 }

app.component.html contanis

<app-menubar></app-menubar>
<app-sidebar></app-sidebar>
<div class="container">
  <router-outlet></router-outlet>
</div>

每当我删除表单标记时，错误就会删除。我不确定是哪里出的错。请帮我解决这个问题。我已经堆放了两天了
 Do：

<form [formGroup]="form">



由于要导入
反应表单模块
，
标记必须具有
表单组

<form [formGroup]="form">