You can use the Session object to store information needed for a particular user-session. Variables stored in the Session object are not discarded when the user jumps between pages in the application; instead, these variables persist for the entire user-session.
The Web server automatically creates a Session object when a Web page from the application is requested by a user who does not already have a session. The server destroys the Session object when the session expires or is abandoned.
One common use for the Session object is to store user preferences. For example, if a user indicates that they prefer not to view graphics, you could store that information in the Session object. For more information on using the Session object, see Managing Sessions in the ASP Applications section.
Note Session state is only maintained for browsers that support cookies.
Session.collection|property|method
| Contents | Contains the items that you have added to the session with script commands. |
| StaticObjects | Contains the objects created with the <OBJECT> tag and given session scope. |
| CodePage | The codepage that will be used for symbol mapping. |
| LCID | The locale identifier. |
| SessionID | Returns the session identification for this user. |
| Timeout | The timeout period for the session state for this application, in minutes. |
| Abandon | This method destroys a Session object and releases its resources. |
Scripts for the following events are declared in the global.asa file.
| Session_OnEnd |
| Session_OnStart |
For more information about these events and the global.asa file, see the Global.asa Reference.
You can store values in the Session object. Information stored in the Session object is available throughout the session and has session scope. The following script demonstrates storage of two types of variables.
<%
Session("username") = "Janine"
Session("age") = 24
%>
However, if you store an object in the Session object and use VBScript as your primary scripting language, you must use the Set keyword. This is illustrated in the following script.
<% Set Session("Obj1") = Server.CreateObject("MyComponent.class1") %>
You can then call the methods and properties exposed by MyComponent.class1 on subsequent Web pages, by using the following.
<% Session("Obj1").MyMethod %>
Or by extracting a local copy of the object and using the following.
<%
Set MyLocalObj1 = Session("Obj1")
MyLocalObj1.MyObjMethod
%>
Another way to create objects with session scope is to use the <OBJECT> tags in the global.asa file.
You cannot, however, store a built-in object in a Session object. For example, each of the following lines would return an error.
<%
Set Session("var1") = Session
Set Session("var2") = Request
Set Session("var3") = Response
Set Session("var4") = Server
Set Session("var5") = Application
%>
Before you store an object in the Session object, you should know what threading model it uses. Only objects marked as both can be stored in the Session object without locking the session to a single thread. For more information, see Selecting a Threading Model in Creating Components for ASP.
If you store an array in a Session object, you should not attempt to alter the elements of the stored array directly. For example, the following script will not work.
<% Session("StoredArray")(3) = "new value" %>
This is because the Session object is implemented as a collection. The array element StoredArray(3) does not receive the new value. Instead, the value is indexed into the collection, overwriting any information stored at that location.
It is strongly recommended that if you store an array in the Session object, you retrieve a copy of the array before retrieving or changing any of the elements of the array. When you are done with the array, you should store the array in the Session object all over again so that any changes you made are saved. This is demonstrated in the following example.
---file1.asp---
<%
'Creating and initializing the array
Dim MyArray()
Redim MyArray(5)
MyArray(0) = "hello"
MyArray(1) = "some other string"
'Storing the array in the Session object
Session("StoredArray") = MyArray
Response.Redirect("file2.asp")
%>
---file2.asp---
<%
'Retrieving the array from the Session Object
'and modifying its second element
LocalArray = Session("StoredArray")
LocalArray(1) = " there"
'printing out the string "hello there"
Response.Write(LocalArray(0)&LocalArray(1))
'Re-storing the array in the Session object
'This overwrites the values in StoredArray with the new values
Session("StoredArray") = LocalArray
%>
The following code assigns the string MyName to a session variable called name, assigns a value to a session variable called year, and assigns an instance of the some.Obj component to a variable called myObj.
Session("name") = "MyName"
Session("year") = 96
Set Session("myObj") = Server.CreateObject("someObj")
%>