asp.net - 为什么会在页面加载前后调用Owin Startup类的Configuration方法？

Question

OWIN 启动类的Configuration 方法在asp.net 身份应用程序中被调用两次。该方法被调用两次，即在服务器端页面加载之前和之后。
我已经找到了一个与之相关的问题( Why is the Configuration method of the SignalR Startup class invoked twice )，但它并没有让我明白什么是代码的预初始化和后初始化。为什么需要它，它会在我的应用程序中出现任何性能问题吗？

这是运行两次的代码:

 public partial class Startup
    {
        public void Configuration(IAppBuilder app)
        {
            ConfigureAuth(app);
        }
    }

下面是配置方法的实现:

 public void ConfigureAuth(IAppBuilder app)
    {
        // Configure the db context, user manager and signin manager to use a single instance per request
        app.CreatePerOwinContext(RavenContext.CreateSession);
        app.CreatePerOwinContext<ApplicationUserManager>(ApplicationUserManager.Create);
        app.CreatePerOwinContext<ApplicationSignInManager>(ApplicationSignInManager.Create);

        // Enable the application to use a cookie to store information for the signed in user
        // and to use a cookie to temporarily store information about a user logging in with a third party login provider
        // Configure the sign in cookie
        app.UseCookieAuthentication(new CookieAuthenticationOptions
        {
            AuthenticationType = DefaultAuthenticationTypes.ApplicationCookie,
            LoginPath = new PathString("/Account/Login"),
            Provider = new CookieAuthenticationProvider
            {
                // Enables the application to validate the security stamp when the user logs in.
                // This is a security feature which is used when you change a password or add an external login to your account.  
                OnValidateIdentity = SecurityStampValidator.OnValidateIdentity<ApplicationUserManager, ApplicationUser>(
                    validateInterval: TimeSpan.FromMinutes(30),
                    regenerateIdentity: (manager, user) => user.GenerateUserIdentityAsync(manager))
            }
        });            
        app.UseExternalSignInCookie(DefaultAuthenticationTypes.ExternalCookie);
}

Answer 1

我不相信它在页面之前和之后加载，但我有类似的情况，我有一个虚拟目录 /preview指向与根目录相同的文件夹。

当我同时按下 F5 时 /preview和 /应用程序被实例化 - 导致对 Startup.Configuration 的两次调用.

我刚刚删除了 /preview虚拟目录，然后它只被调用一次。

在 Startup 中放置断点可能很困难，因此请尝试这样的操作以准确查看启动被初始化的次数。

public class Startup
{
    public static Guid GlobalGuid { get; private set; }

    static Startup()
    {
        GlobalGuid = Guid.NewGuid();
    }

    public void Configuration(IAppBuilder app)
    {           
       File.AppendAllLines(@"c:\temp\Startup.txt", 
                           new[] { DateTime.Now + " initialized - " + GlobalGuid });
    }
}