Session 和 HttpContext.Current.Session 的区别 [英] Difference between Session and HttpContext.Current.Session

问题描述

Session 和 HttpContext.Current.Session 对象有什么区别?

What is the difference between Session and HttpContext.Current.Session object?

推荐答案

这里有点晚了，但这是我刚刚发现的东西.

A little late here, but here's something I just discovered.

@Phillipe Leybaert 和@CSharpAtl 都是错误的.HttpApplication 的 Session 属性表现出与 HttpContext.Current.Session 属性不同的行为.它们都将返回对同一个 HttpSessionState 实例的引用 如果 一个可用.当没有可用于当前请求的 HttpSessionState 实例时，它们的不同之处在于它们所做的.

@Phillipe Leybaert and @CSharpAtl are both incorrect. HttpApplication's Session property exhibits different behaviour than does that of the property HttpContext.Current.Session. They will both return a reference to the same HttpSessionState instance if one is available. They differ in what they do when there is no instance of HttpSessionState available for the current request.

并非所有 HttpHandler 都提供会话状态.为此，HttpHandler 必须实现[一个或两个?]标记接口IRequiresSessionState或IReadOnlySessionState.

Not all HttpHandlers provide session state. To do so, the HttpHandler must implement [one or both?] the marker interfaces IRequiresSessionState or IReadOnlySessionState.

HttpContext.Current.Session 如果没有可用的会话，则只返回 null.

HttpContext.Current.Session simply returns null if there is no session available.

HttpApplication 对 Session 属性的实现抛出一个 HttpException 消息 Session state is not available in this context. 而不是返回 null 引用.

The HttpApplication's implementation of the Session property throws an HttpException with the message Session state is not available in this context. rather than returning a null reference.

一些没有实现会话的 HttpHandler 示例是通常静态资源(例如图像和 CSS 文件)的默认处理程序.在这种情况下(如在 global.asax 事件处理程序中)对 HttpApplication 的 Session 属性的任何引用都将导致 HttpException 被抛出.

Some examples of HttpHandler that do not implement session are the default handlers for normally static resources, such as image and CSS files. Any reference to the HttpApplication's Session property in such cases (as in global.asax event handlers) will result an HttpException being thrown.

不用说，意外的 HttpException 提供了一个 WTF?！如果你不期待它，那一刻.

Needless to say, the unexpected HttpException provides a WTF?! moment if you're not expecting it.

HttpApplication 类的 Session 属性是这样实现的(来自反射器):

The Session property of the HttpApplication class is implemented thus (from Reflector):

[Browsable(false), DesignerSerializationVisibility(DesignerSerializationVisibility.Hidden)]
public HttpSessionState Session
{
  get
  {
    HttpSessionState session = null;

    if (this._session != null)
    {
        session = this._session;
    }
    else if (this._context != null)
    {
        session = this._context.Session;
    }

    if (session == null)
    {
        throw new HttpException(SR.GetString("Session_not_available"));
    }

    return session;
  }
}

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