خطای This likely means that the library (@angular/common/http) which declares HttpClient has not been processed correctly by ngcc,

3/27/2020 MVC
89

برای اینکه بتونم اطلاعات رو در پروژه انگولار از بانک اطلاعاتی بخونم یه service  اضافه کردم و برای استفاده لازم بود این خط کد رو import کنم 

import {HttpClientModule, HttpClient } from '@angular/common/http';

و ردر service هم همینطور 

import { HttpHeaders, HttpClient } from '@angular/common/http';

اما زمانی پروژه رو اجرا کردم به ا ین خطا برخوردم 

 This likely means that the library (@angular/common/http) which declares HttpClient has not been processed correctly by ngcc, or is not compatible with Angular Ivy. Check if a newer version of the library is available, and update if so. Also consider checking 
with the library's authors to see if the library is expected to be compatible with Ivy.

 

 

برای  رفع این خطا ا HttpClient  رو از app.model.ts  حذف کردم و فقط همونHttpClientModul  را نگه داشتم و به جای آن HttpClient  را در News.Service.ts اضافه کردم 

کل پروسه این شکلی شد 

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';

import {HttpClientModule } from '@angular/common/http';
import { FormsModule } from '@angular/forms';
import { AppRoutingModule } from './app-routing.module';

import { AppComponent } from './app.component';
import { BrowserAnimationsModule } from '@angular/platform-browser/animations';






@NgModule({
  declarations: [
    AppComponent,
    HomeNewsComponent,

  ],
  imports: [
    BrowserModule,
    BrowserAnimationsModule,

    HttpClientModule,


],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

و در service 

import { Injectable } from '@angular/core';
import {NewsModel} from '../Models/News.Model';
import { HttpHeaders, HttpClient } from '@angular/common/http';
import { Observable } from 'rxjs';

const httpOption = {headers: new HttpHeaders({'content-Type': 'application/json'})};
const newsUrl = 'https://localhost:5001/api/News';

@Injectable({
  providedIn: 'root'
})
export class NewsService {

  selectedNews: NewsModel;
  NewsList: NewsModel[];

  constructor(private http: HttpClient) { }

  getNewsList(): Observable<NewsModel[] > {
return this.http.get<NewsModel[]>(newsUrl);
  }
}