title: 'ConfigurationBuilder' does not contain a definition for 'AddJsonFile'
body: <p>I have the following error:</p>
  
  <p>Program.cs(15,72): error CS1061: 'ConfigurationBuilder' does not contain a definition for 'AddJsonFile' and no accessible extension method 'AddJsonFile' accepting a first argument of type 'ConfigurationBuilder' could be found (are you missing a using directive or an assembly </p>
  
  <p>The project is a dotnet core app, console application, using Azure Search SDK</p>
  
  <p>The line of error is below:</p>
  
  <pre><code>using System;
  using System.Linq;
  using System.Threading;
  using Microsoft.Azure.Search;
  using Microsoft.Azure.Search.Models;
  using Microsoft.Extensions.Configuration;
  using Microsoft.Spatial;
  
  namespace DemoSearchIndexer
  {
      class Program
      {
          static void Main(string[] args)
          {
              IConfigurationBuilder builder = new ConfigurationBuilder().AddJsonFile("appsettings.json");
              IConfigurationRoot configuration = builder.Build();
  </code></pre>