Define variable as static - changes even launching new browser

[Johnny Luner]

I have a base class (root.cs) and all my pages inherits from it. When I
access default_1.aspx, it changes the base class variable intentionally.
Now, when I close the browser launch a new I.E. to access default_2.aspx,
it shows "changed!!" on my screen! I assume launching new browser would
start a new instance everything. Can anyone explain why? thanks...

------------------------------------------------------------
root.cs (this file is compiled and put in /bin directory)
------------------------------------------------------------

using System;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;

namespace company {
public class main : Page {
public static String my_string = "hello world";
}
}

------------------------------------------------------------
default_1.aspx
------------------------------------------------------------
<%@ Page Inherits="company.main" %>
<script language="c#" runat="server">
void Page_load(Object sender, EventArgs e) {
my_string = "changed!!!";
}
</script>

 

[Jon Skeet [C# MVP]]

I have a base class (root.cs) and all my pages inherits from it. When I
access default_1.aspx, it changes the base class variable intentionally.
Now, when I close the browser launch a new I.E. to access default_2.aspx,
it shows "changed!!" on my screen! I assume launching new browser would
start a new instance everything. Can anyone explain why? thanks...

Why would you expect starting a new browser to create a new a static
variable? A static variable belongs to the type - it has no concept of
a session or anything like that. You have one variable for as long as
the type sticks around. When the AppDomain is unloaded and reloaded,
that'll be a new variable - but until then, you'll have the one shared
variable.

It sounds like you're *really* after session data - look it up in an
ASP.NET tutorial.

 

[Johnny Luner]

Thanks!! that helps..

Why would you expect starting a new browser to create a new a static
variable? A static variable belongs to the type - it has no concept of
a session or anything like that. You have one variable for as long as
the type sticks around. When the AppDomain is unloaded and reloaded,
that'll be a new variable - but until then, you'll have the one shared
variable.

It sounds like you're *really* after session data - look it up in an
ASP.NET tutorial.

 

[Martin Dechev]

The static fields are fields of the Type, not the class instance:

http://msdn.microsoft.com/library/en-us/csref/html/vclrfStaticPG.asp

Since the Type is the same for the lifetime of the application (hence the
multiple different instances a class can have) they preserve the last value
they have been assigned to.

Hope this helps
Martin

 

[Dilip Krishnan]

Static variables by definition are a single instance for the scope of
the *type*. They are not object instances. Hope that helps