Web API 源码剖析之全局配置

//
// 摘要:
// 为 ASP.NET 应用程序提供全局 System.Web.Http.HttpConfiguration。
public static class GlobalConfiguration
{
public static HttpConfiguration Configuration { get; }
public static HttpMessageHandler DefaultHandler { get; }
//
// 摘要:
// 获取全局 System.Web.Http.HttpServer。
//
// 返回结果:
// 全局 System.Web.Http.HttpServer。
public static HttpServer DefaultServer { get; }

public static void Configure(Action<HttpConfiguration> configurationCallback);
}

//延迟加载

private static Lazy<HttpConfiguration> _configuration = CreateConfiguration();

//只读配置属性

public static HttpConfiguration Configuration
{
get { return _configuration.Value; }
}

private static Lazy<HttpConfiguration> CreateConfiguration()
{
return new Lazy<HttpConfiguration>(() =>
{
HttpConfiguration config = new HttpConfiguration(new HostedHttpRouteCollection(RouteTable.Routes));
ServicesContainer services = config.Services;
Contract.Assert(services != null);
services.Replace(typeof(IAssembliesResolver), new WebHostAssembliesResolver());
services.Replace(typeof(IHttpControllerTypeResolver), new WebHostHttpControllerTypeResolver());
services.Replace(typeof(IHostBufferPolicySelector), new WebHostBufferPolicySelector());
services.Replace(typeof(IExceptionHandler),
new WebHostExceptionHandler(services.GetExceptionHandler()));
return config;
});
}