当Session [& quot; something&]]引发NullReferenceException时，如何自动调用方法?

问题描述

我将在我的应用程序中大量使用Session["firmaid"].当有人登录到我的系统时，将设置此值.

I am going to be using Session["firmaid"] quite alot in my application. This value is set when someone logs in to my system.

如果发生某种情况，并且该值从Session中丢失，我想以某种方式拥有一个全局方法，如果该方法抛出NullReferenceException.

If something happens, and this value is lost from the Session, i would like to somehow have a global method that will get it, if it throws a NullReferenceException.

我该怎么做?

当前，我的解决方案是每次使用Session["firmaid"]时都尝试捕获，然后执行将Firmaid放入Session的方法(如果抛出Exception的话).

Currently, my solution is to try and catch every time i use Session["firmaid"], then execute the method that will put firmaid in the Session, if it throws an Exception.

有更简单的方法吗?

推荐答案

您不必每次都尝试/捕获，而可以将对会话的访问权包装在强类型的类中，然后通过此包装器访问会话.

Instead of try/catching everytime you could wrap the access to the session in a strongly typed class and then access the session through this wrapper.

甚至编写扩展方法:

public static class SessionExtensions
{
    public static string GetFirmaId(this HttpSessionStateBase session)
    {
        var firmaid = session["firmaid"] as string;
        if (string.IsNullOrEmpty(firmaid))
        {
            // TODO: call some method, take respective actions
        }      
        return firmaid;
    }
}

，然后在您的代码中代替:

and then in your code instead of:

try
{
    var firmaid = Session["firmaid"];
    // TODO: do something with the result
}
catch (Exception ex)
{
    // TODO: call some method, take respective actions
}

使用:

var firmaid = Session.GetFirmaId();
// TODO: do something with the result

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