c# - HttpContext.Current.Session - NullReferenceException

Question

我在 MVC 4 ASP.NET 项目的设置类中遇到了对象引用未设置为对象实例错误，它获取了我的当前 session 详细信息。每次我浏览页面时，该变量都会抛出 NullReferenceException，并且不明白为什么，因为它之前运行完美，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 null 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。

以后学习使用调试，这样的错误你会很快解决的!