ASP.NET Core 2 and Angular 5

Adding ReactiveFormsModule

From Solution Explorer, open the app.module.shared.ts file and add the following (new lines are highlighted):

import { NgModule } from '@angular/core';import { CommonModule } from '@angular/common';import { FormsModule, ReactiveFormsModule } from '@angular/forms';[...]    imports: [        CommonModule,        HttpClientModule,        FormsModule,        ReactiveFormsModule,[...]

That's it, now we're good to go.