Change List<Action> to Action (#1480)

Author: alfredmyers

src/Microsoft.AspNetCore.Hosting/WebHostBuilder.cs

@@ -25,22 +25,20 @@ namespace Microsoft.AspNetCore.Hosting
  public class WebHostBuilder : IWebHostBuilder
  {
  private readonly HostingEnvironment _hostingEnvironment;
- private readonly List<Action<WebHostBuilderContext, IServiceCollection>> _configureServicesDelegates;
+ private Action<WebHostBuilderContext, IServiceCollection> _configureServices;
 
  private IConfiguration _config;
  private WebHostOptions _options;
  private WebHostBuilderContext _context;
  private bool _webHostBuilt;
- private List<Action<WebHostBuilderContext, IConfigurationBuilder>> _configureAppConfigurationBuilderDelegates;
+ private Action<WebHostBuilderContext, IConfigurationBuilder> _configureAppConfigurationBuilder;
 
  /// <summary>
  /// Initializes a new instance of the <see cref="WebHostBuilder"/> class.
  /// </summary>
  public WebHostBuilder()
  {
  _hostingEnvironment = new HostingEnvironment();
- _configureServicesDelegates = new List<Action<WebHostBuilderContext, IServiceCollection>>();
- _configureAppConfigurationBuilderDelegates = new List<Action<WebHostBuilderContext, IConfigurationBuilder>>();
 
  _config = new ConfigurationBuilder()
  .AddEnvironmentVariables(prefix: "ASPNETCORE_")
@@ -111,12 +109,7 @@ public IWebHostBuilder ConfigureServices(Action<IServiceCollection> configureSer
  /// <returns>The <see cref="IWebHostBuilder"/>.</returns>
  public IWebHostBuilder ConfigureServices(Action<WebHostBuilderContext, IServiceCollection> configureServices)
  {
- if (configureServices == null)
- {
- throw new ArgumentNullException(nameof(configureServices));
- }
-
- _configureServicesDelegates.Add(configureServices);
+ _configureServices += configureServices;
  return this;
  }
 
@@ -131,12 +124,7 @@ public IWebHostBuilder ConfigureServices(Action<WebHostBuilderContext, IServiceC
  /// </remarks>
  public IWebHostBuilder ConfigureAppConfiguration(Action<WebHostBuilderContext, IConfigurationBuilder> configureDelegate)
  {
- if (configureDelegate == null)
- {
- throw new ArgumentNullException(nameof(configureDelegate));
- }
-
- _configureAppConfigurationBuilderDelegates.Add(configureDelegate);
+ _configureAppConfigurationBuilder += configureDelegate;
  return this;
  }
 
@@ -272,10 +260,7 @@ private IServiceCollection BuildCommonServices(out AggregateException hostingSta
  .SetBasePath(_hostingEnvironment.ContentRootPath)
  .AddConfiguration(_config);
 
- foreach (var configureAppConfiguration in _configureAppConfigurationBuilderDelegates)
- {
- configureAppConfiguration(_context, builder);
- }
+ _configureAppConfigurationBuilder?.Invoke(_context, builder);
 
  var configuration = builder.Build();
  services.AddSingleton<IConfiguration>(configuration);
@@ -329,10 +314,7 @@ private IServiceCollection BuildCommonServices(out AggregateException hostingSta
  }
  }
 
- foreach (var configureServices in _configureServicesDelegates)
- {
- configureServices(_context, services);
- }
+ _configureServices?.Invoke(_context, services);
 
  return services;
  }