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Publisher19.4 Methods Reference
| Abandon |
Session.Abandon( ) |
and causes the Session.End event to be fired.
Parameters
None
Example
The example examines the IsNewSession property to determine if the
current request has resulted in a new session. If so, it adds a value
to the Session collection and then displays a message indicating that
a new session was created. If a session already exists, the example
displays a button that, when clicked, causes a postback. This
postback results in the Session.Abandon method being called and the
session terminated:
If Not IsPostBack
If Session.IsNewSession Then
Session("foo") = "foo"
Message.Text = "The current Session (SessionID: " & _
Session.SessionID & ") was created with this request."
Else
Message.Text = "Click the button to abandon the current session."
Dim AbandonButton As New Button
AbandonButton.Text = "Abandon Session"
myForm.Controls.Add(AbandonButton)
End If
Else
Session.Abandon( )
Message.Text = "Session abandoned."
End If
In order for the postback to work correctly, a server-side form needs
to be added within the <body> tags, as shown
below:
<form id="myForm" runat="server">
<asp:label id="Message" runat="server"/>
</form>
Notes
The Abandon method is very important for controlling resource usage
in ASP.NET applications that use session state. If you use session
state for storing application data, you should implement a logout
method that calls Session.Abandon and make it as easy as possible for
your users to access this method (via a button or link on each page).
Implementing this method will help prevent resources from being
consumed for longer than necessary when a user has already quit using
the application.Note that the End event will be fired only when session state has
been configured for in-process operation.
| Add |
Session.Add(ByVal name As String, ByVal value As Object) |
Parameters
- name
A string argument containing the name that will be used to refer to
the new item.- value
An object argument containing the value of the new item.
Example
The example declares a local variable, sets its value, and adds an
item to the Session collection with the value of the local variable:
Sub Page_Load( )
Dim myBaz As String = "baz"
Session.Add("baz", myBaz)
Dim I as Integer
For I = 0 To Session.Count - 1
Message.Text &= CStr(Session(I)) & "<br/>"
Next
End Sub
Notes
The Add method, which is new in ASP.NET, provides a technique for
adding items to the Session collection, which is consistent with the
technique used for adding items to other .NET collections.
| Clear |
Session.Clear( ) |
Parameters
None
Example
The example clears the contents of the Session collection and writes
a message to the Text property of the Message label control that
includes the current count of the collection, which should be 0:
Sub Page_Load( )
Session.Clear( )
Message.Text = "There are " & Session.Count & _
" items in the Session collection."
End Sub
Notes
The Clear method, which is new for ASP.NET, clears only the contents
of the Session collection itself. It does not clear the contents of
the StaticObjects collection.
| CopyTo |
Session.CopyTo(ByVal array As Array, ByVal index As Integer) |
array.
Parameters
- array
An array argument that will receive the session collection values.- index
An integer argument specifying the point in the array at which to
begin copying.
Example
The example checks to ensure that at least one item is in the Session
collection, and if there is, it creates a local object array, copies
the contents of the Session collection to it, and displays the value
of the first item:
Sub Page_Load( )
If Session.Count > 0 Then
Dim myArray As Array = Array.CreateInstance(GetType(Object), _
Session.Count)
Session.CopyTo(myArray, 0)
Message.Text = "The first item in the array is: " & _
CStr(myArray(0))
End If
End Sub
Notes
The CopyTo method is useful if you have a large number of items
stored in the Session collection. In such cases, accessing values
from a local array variable may be faster and more efficient than
accessing the values from the Session collection, particularly when
session state is configured to run out of process. The improved
efficiency and performance comes at the cost of ease of use, since
arrays do not provide the same feature richness as the Session
collection.
| Remove |
Session.Remove(ByVal name As String) |
Parameter
- name
A string argument containing the name (key) of the item to remove.
Example
The example determines whether the item with the key
"foo" exists in
the Session collection and if it does, removes the item and displays
an appropriate message:
Sub Page_Load( )
If Not Session("foo") Is Nothing Then
Session.Remove("foo")
Message.Text = "Item 'foo' was removed."
Else
Message.Text = "Item 'foo' does not exist."
End If
End Sub
Notes
The Remove method is provided for backward compatibility with classic
ASP. In classic ASP, this method was accessed through the Contents
collection. In ASP.NET, this method can be accessed either directly,
as shown above, or through the Contents collection.
| RemoveAll |
Session.RemoveAll( ) |
Parameters
None
Example
The example checks to ensure that at least one item is in the Session
collection (although if RemoveAll is called on an empty Session
collection, no error will occur), and if it is, it clears the
collection by calling the RemoveAll method:
Sub Page_Load( )
If Session.Count > 0 Then
Session.RemoveAll( )
Message.Text = "Session collection cleared."
Else
Message.Text = "Session collection is already empty."
End If
End Sub
Notes
The RemoveAll method is provided for backward compatibility with
classic ASP. In classic ASP, this method was accessed through the
Contents collection. In ASP.NET, this method can be accessed either
directly, as shown above, or through the Contents collection.RemoveAll has the same effect as calling the Clear method and like
Clear, it clears the contents of the Session collection, but does not
remove Session-scoped objects from the StaticObjects collection.
| RemoveAt |
Session.RemoveAt(ByVal index As Integer) |
companion to the Remove method, which removes an item by key.
Parameter
- index
An integer argument containing the index location of the item to
remove from the Session collection.
Example
Sub Page_Load( )
If Session.Count > 0 Then
Session.RemoveAt(0)
Message.Text = "The item at index 0 was removed."
Else
Message.Text = "The item at index 0 does not exist."
End If
End Sub
Notes
The RemoveAt method allows items to be removed from the Session
collection by index rather than by key. As in the example above, the
items that follow the removed item will shift one position in the
collection when the item is removed. If you remove an item by index
and call RemoveAt again with the same index, you will remove the item
that immediately followed the original removed item.
