与asp.net应用程序中的类共享一个全局变量

Question

I am developping an asp.net application. I have a page called "home.aspx" which contains 2 buttons called "button1" and "button2". Each button has a onclick method, respectively called "Button1_click" and "Button2_click". My goal is to share a common variable between these 2 methods, so basically I tried to add a property to the class associated to my page like this :

public partial class Home : Syste.Web.UI.Page
{
    private int myproperty=0;

    protected void Button1_Click(object sender, EventArgs e)
    {
        myproperty++;
    }

    protected void Button2_Click(object sender, EventArgs e)
    {
        myproperty++;  
    }
}

With this code, I was thinking that the "private int myproperty=0" would be called only the first time I load and get to the page. And then when I would be on the page, if I click on button1 or button2 the myproperty would just be incrementated by one. But when I am debugging, I see that each time I click on button1 or button2 the "private int myproperty=0" is called again which I don't understand. Is anyone has a solution?

Thanks in advance for your help.

Answer 1

In ASP.NET if you want use global variables you'll have to use the Session object(if the variable is different for every single user, like count how many time a user click a Button) or Application object(If the variable is common to all the users like count how much user visit your site). Example:

//Set variable
Session["myVariable"] = value
//Get variable
var myVariable = Session["myVariable"]

The syntax is equal for Application just replace Session with Application

Answer 2

Make your variable static

Like this

    public partial class Home : Syste.Web.UI.Page
   {
    private Static int myproperty;

    protected void Button1_Click(object sender, EventArgs e)
    {
        //You can access myproperty here (same copy)
    }

    protected void Button2_Click(object sender, EventArgs e)
    {
         //You can access myproperty here (same copy)
    }
}

Answer 3

You can use Session as below

private int Count
{
  get 
   {
     if (Session["Count"] == null)
     {         Session["Count"] = 0; return 0;      }
     else 
        return (int)Session["Count"] ; 
   }
   set
   {
      Session["Count"] = value;
   }
} 

protected void Page_Load(object sender, EventArgs e)     
{
    if(!IsPostBack)
        Count = 0; 
}

protected void Button1_Click(object sender, EventArgs e)
{
     Count++; 
}

protected void Button2_Click(object sender, EventArgs e)
{
     Count++; 
}

Answer 4

How you want to share the value of the variable myproperty?

-If you want to reuse the value of myproperty per window you need to store the value in the vewstate: http://msdn.microsoft.com/en-us/library/ms227551%28v=vs.85%29.aspx

Another way is to use a asp.net webcontrol hiddenfiled to store the value.

-If you want to reuse the value for session, you can store the value in the session (Session["myproperty"])

-If you want to share the value with all the users you can use the application: http://msdn.microsoft.com/en-us/library/94xkskdf%28v=vs.100%29.aspx

Answer 5

as Ben Robinson said you have to persist that value somewhere. An easy way is to use Session:

1. Create a "const string" variable in the class to hold the session index like:

   const string MY_PROPERTY = "MyProperty";

2. then whenever you want to store or read the value use:

   //to store Session[Home.MY_PROPERTY] = int.parse(Session[Home.MY_PROPERTY])+1; //to read int myVariable = int.parse(Session[Home.MY_PROPERTY])

you can also create a property in your class like:

const string MY_PROPERTY = "MyProperty";
public int MyProperty
{
    get
    {
        if (Session[Home.MY_PROPERTY] == null)
        {
            return 0;
        }
        else
        {
            int iValue = 0;
            if (int.TryParse(Session[Home.MY_PROPERTY].ToString(), out iValue))
                return iValue;
            else
                return 0;
        }
    }
    set
    {
        Session[Home.MY_PROPERTY] = value;
    }
}

Answer 6

Only the postback check, before the increment, can resolve the problem. Add following code before increment.

if(!IsPostBack)