title: Entity Framework Core: DbContextOptionsBuilder does not contain a definition for 'usesqlserver' and no extension method 'usesqlserver'
body: <p>I am new to EF core and I'm trying to get it to work with my ASP.NET Core project.</p>
  <p>I get the above error in my <code>startup.cs</code> when trying configure the <code>DbContext</code> to use a connection string from config. I am following <a href="https://docs.microsoft.com/en-us/aspnet/core/data/ef-mvc/intro" rel="noreferrer">this tutorial</a>.</p>
  <p>The problematic code is in <code>startup.cs</code>:</p>
  <pre class="lang-cs prettyprint-override"><code>using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Threading.Tasks;
  using Microsoft.AspNetCore.Builder;
  using Microsoft.AspNetCore.Hosting;
  using Microsoft.AspNetCore.SpaServices.Webpack;
  using Microsoft.Extensions.Configuration;
  using Microsoft.Extensions.DependencyInjection;
  using Microsoft.Extensions.Logging;
  using Microsoft.EntityFrameworkCore;
  using tracV2.models;
  using tracV2.data;
  
  namespace tracV2
  {
      public class Startup
      {
          // This method gets called by the runtime. Use this method to add services to the container.
          public void ConfigureServices(IServiceCollection services)
          {
              // Add framework services.
              services.AddMvc();
  
              services.AddSingleton&lt;IConfiguration&gt;(Configuration);
  
              string conn = Configuration.GetConnectionString(&quot;optimumDB&quot;);
  
              services.AddDbContext&lt;tracContext&gt;(options =&gt; options.usesqlserver(conn));
          }
  </code></pre>
  <p>The <code>UseSqlServer</code> method is recognized if I put it directly into the context:</p>
  <pre class="lang-cs prettyprint-override"><code>using System;
  using System.Collections.Generic;
  using System.Linq;
  using System.Threading.Tasks;
  using Microsoft.EntityFrameworkCore;
  
  namespace tracV2.data
  {
      public class tracContext : DbContext
      {
          protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
          {
              optionsBuilder.UseSqlServer(&quot;myrealconnectionstring&quot;);
          }
  </code></pre>
  <p>All my research online points to missing references, but I can't seem to find out which one I am missing (<a href="https://i.stack.imgur.com/2cbxl.png" rel="noreferrer">see image</a>).</p>