angular 4/5 database connection different

import { Injectable } from '@angular/core';

//import {Http, Headers, RequestOptions } from '@angular/http'; //angular 4

import { HttpClient,HttpHeaders } from '@angular/common/http';  // angular 5

import 'rxjs/Rx';

@Injectable()

export class ApiService{

  //public base:string="http://www.myapi.com/v2/";

  public base:string="http://localhost:1028/";

  constructor(public http:HttpClient){

  }

        /*   angular 4   */

    let headers = new Headers(

 { 'Content-Type':'application/json'}

 // { 'Content-Type': 'Access-Control-Allow-Headers' }

 // { 'Content-Type': 'application/x-www-form-urlencoded; charset=UTF-8' }

 );

   let options = new RequestOptions({ headers: headers });

// angular 5

//    let headers = new HttpHeaders();

//    headers = headers.set('Content-Type', 'application/json; charset=utf-8');

    let headers:any = new HttpHeaders(

    {'Content-Type':'application/json; charset=utf-8'}

    );

     return this.http.post(this.base + url , data , headers )

                   .toPromise()

                   .then( )

                   .catch()

  }

  get(){