Asp.net “Global” variables

问题

I'm writing a page in ASP.NET and am having problems following the cycle of initialization on postbacks:

I have (something akin to) the following:

public partial class MyClass : System.Web.UI.Page
{
    String myString = "default";

    protected void Page_Init(object o, EventArgs e)
    {
        myString = Request["passedString"];
        //note that I've tried to set the default here in Init on NULL...
    }

    protected void Page_Load(object o, EventArgs e)
    {
         if(!Postback)
         {
             //code that uses myString....
         }
         else
         {
            //more code that uses myString....
         }
    }
}

And what's happening is that my code picks up the "passedString" just fine, but for some reason, on postback, it resets to the default value - even if I put the assignment of the default in the Page_Init code... which makes me wonder what's going on..

Any help?

回答1:

Your class member variables do not live on once the response is sent to the browser. Try using the Session object instead:

public partial class MyClass : System.Web.UI.Page
{    

    protected void Page_Init(object o, EventArgs e)
    {
        Session["myString"] = Request["passedString"];
        //note that I've tried to set the default here in Init on NULL...
    }

    protected void Page_Load(object o, EventArgs e)
    {
         string myString = (string) Session["myString"];

         if(!Postback)
         {
             // use myString retrieved from session here
         }
         else
         {
            //more code that uses myString....
         }
    }
}

回答2:

I feel your pain Matt. I asked a similar question a little while ago:

For a further understanding of the Page Life Cycle check out this question: What is the 'page lifecycle' of an ASP.NET WebForm?

来源：https://stackoverflow.com/questions/690452/asp-net-global-variables