HttpContext.Current.Session - NullReferenceException

Question

我在 MVC 4 ASP.NET 项目的 Settings 类中遇到了 Object Reference not set to an instance 错误，该类获取了我的当前会话详细信息。每次我浏览一个页面时，该变量都会抛出 NullReferenceException，并且无法理解为什么，因为它以前可以完美运行，没有任何问题。

namespace TracerCRM.Web
{
    public class Settings
    {
        public static Settings Current
        {
            get
            {
                Settings s = HttpContext.Current.Session["Settings"] as Settings;
                if (s == null)
                {
                    s = new Settings();
                    HttpContext.Current.Session["Settings"] = s;
                }

                return s;
            }
        }
    }
}

我尝试了以下我在研究过程中遇到的事情：

1："HttpContext.Current.Session" vs Global.asax "this.Session"

2：Rare System.NullReferenceException show up for a HttpContext.Current.Session["courseNameAssociatedWithLoggedInUser"] that was previously populated?

3：The Session object is null in ASP.NET MVC 4 webapplication once deployed to IIS 7 (W 2008 R2)

4：Log a user off when ASP.NET MVC Session expires

5：Login Session lost sometimes when redirect to action in asp.net mvc 3

以上都不适合我。

Answer 1

        public static Settings Current
        {
            get
            {
                if(HttpContext.Current.Session == null)
                {
                     Settings s = new Settings();
                     return s;
                }
                if (HttpContext.Current.Session["Settings"] == null)
                {
                    Settings s = new Settings();
                    HttpContext.Current.Session["Settings"] = s;
                    return s;
                }

                return (Settings)HttpContext.Current.Session["Settings"];
            }
        }

当 Session["Settings"] 为空时，您将其包装到 Setting 类。如果您像这样更改代码，它应该可以工作。

以后学习使用debug，这样的错误你会很快解决的！

Answer 2

添加这个 Global.asax.cs

using System.Web.SessionState;

protected void Application_PostAuthorizeRequest()
{
    System.Web.HttpContext.Current.
        SetSessionStateBehavior(System.Web.SessionState.SessionStateBehavior.Required);
}