title: WebHostBuilder.Build() MissingMethodException in .NET Core migrated solution
body: <p>I'm migrating a solution built with .NET Core SDK 1.0.0-preview2-1-003177 because  I want to use it in Visual Studio 2017. I use the dotnet migrate command from .NET Core SDK 1.0.1, it goes well, it compiles. When I run the web part with IIS Express the classic <em>Program.cs</em> containing</p>
  
  <pre><code>var host = new WebHostBuilder()
      .UseKestrel()
      .UseContentRoot(Directory.GetCurrentDirectory())
      .UseIISIntegration()
      .UseStartup&lt;Startup&gt;()
      .Build();
  
  host.Run();
  </code></pre>
  
  <p>crashes at <strong>Build()</strong> with this exception</p>
  
  <blockquote>
    <p>System.MissingMethodException: 'Method not found:
    'System.IServiceProvider
    Microsoft.Extensions.DependencyInjection.ServiceCollectionContainerBuilderExtensions.BuildServiceProvider(Microsoft.Extensions.DependencyInjection.IServiceCollection)'.'</p>
  </blockquote>
  
  <p>I can't find the reason at all.</p>