.net - Global.asax ASP.Net Web API 中的 GlobalConfiguration.Configuration.EnsureInitialized() 是什么

Question

在我的WebApi项目下，我不知道这一行是什么GlobalConfiguration.Configuration.EnsureInitialized()在那里做 Global.asax Application_Start()方法。没有这个，即使每件事都运行良好。那这是为什么呢？

有必要在这里吗？如果是，那为什么？任何人都可以解释其
详细需求和目的 .

protected void Application_Start()
{   
    AreaRegistration.RegisterAllAreas();
    FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
    RouteConfig.RegisterRoutes(RouteTable.Routes);

    ////////////      What is this for   ////////////////
    GlobalConfiguration.Configuration.EnsureInitialized();
}

NOT A DUPLICATE : In stack overflow many people suggest to use EnsureInitialized().But Why to use it? Where it comes from? Is it part of webApi2 or something else? These are are the things I want to know. MSDN itself has no explanation for this.

Answer 1

每 MSDN :

HttpConfiguration.EnsureInitialized Method

Invoke the Intializer hook. It is considered immutable from this point forward. It's safe to call this multiple times.

更多信息
如 this answer指出，这很可能在某个时候被放入您的应用程序中，因为 Web API 应该在 Web API v1 与 Web API v2 中注册的方式发生了变化。
升级 Web API 后未进行更改的任何人都会收到错误消息:

The object has not yet been initialized. Ensure that HttpConfiguration.EnsureInitialized() is called in the application's startup code after all other initialization code.

不幸的是，错误消息中给出的解决方案具有误导性。你是什​​么 actually supposed to change while upgrading from V1是替换这一行:

WebApiConfig.Register(GlobalConfiguration.Configuration);

用这一行:

GlobalConfiguration.Configure(WebApiConfig.Register);

后一种方法在内部调用 EnsureInitialized所以你不必从你的启动代码。
我注意到您的配置中没有这些 Web Api 初始化程序中的任何一个，因此我建议您按如下方式更改启动:

protected void Application_Start()
{   
    AreaRegistration.RegisterAllAreas();
    FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
    GlobalConfiguration.Configure(WebApiConfig.Register);
    RouteConfig.RegisterRoutes(RouteTable.Routes);
}