Transferring Object from Session Variable to New Class Object???

[Don Miller]

I am using a Session variable to hold a class object between ASP.NET pages
(in VB). In my constructor I check to see if the Session variable exists,
and if it doesn't, I create one and populate it with "Me". But if the
Session variable already exists, I would like the new object be populated
with everything from the object stored in the Session variable. Ideally, I'd
like to retrieve the object from the Session variable and assign it to "Me"
(e.g. Me = , but that is not possible, and instead it seems that I have to
populate the new object property by property (see below). Is there a more
efficient way to "clone" the object held in the Server variable to a new
object?

Thanks.

Imports ....

Public Class SessionVarObject

Private Const SESSION_VARIABLE As String = "SessionVarObject"

Private _name As String
... other private variables

Public Property Name() As String
Get
Return _name
End Get
Set(ByVal value As String)
_name = value
saveObjectToSession(Me)
End Set
End Property

Public Sub New()
If IsNothing(HttpContext.Current.Session(SESSION_VARIABLE)) Then
saveObjectToSession(Me)
Else
populateMeFromSession()
End If
End Sub

Private Sub saveObjectToSession(ByVal objToSave)
HttpContext.Current.Session(SESSION_VARIABLE) = objToSave
End Sub

Private Sub populateMeFromSession()
Dim obj As SessionVarObject =
CType(HttpContext.Current.Session(SESSION_VARIABLE), SessionVarObject)
' I would prefer to just use one statement
' Me = obj
' instead of delineating each private variable for each property
Me._name = obj._name
... etc.
End Sub

 

[=?ISO-8859-1?Q?G=F6ran_Andersson?=]

I am using a Session variable to hold a class object between ASP.NET pages
(in VB). In my constructor I check to see if the Session variable exists,
and if it doesn't, I create one and populate it with "Me". But if the
Session variable already exists, I would like the new object be populated
with everything from the object stored in the Session variable. Ideally, I'd
like to retrieve the object from the Session variable and assign it to "Me"
(e.g. Me = , but that is not possible, and instead it seems that I have to
populate the new object property by property (see below). Is there a more
efficient way to "clone" the object held in the Server variable to a new
object?

Thanks.

Imports ....

Public Class SessionVarObject

Private Const SESSION_VARIABLE As String = "SessionVarObject"

Private _name As String
... other private variables

Public Property Name() As String
Get
Return _name
End Get
Set(ByVal value As String)
_name = value
saveObjectToSession(Me)
End Set
End Property

Public Sub New()
If IsNothing(HttpContext.Current.Session(SESSION_VARIABLE)) Then
saveObjectToSession(Me)
Else
populateMeFromSession()
End If
End Sub

Private Sub saveObjectToSession(ByVal objToSave)
HttpContext.Current.Session(SESSION_VARIABLE) = objToSave
End Sub

Private Sub populateMeFromSession()
Dim obj As SessionVarObject =
CType(HttpContext.Current.Session(SESSION_VARIABLE), SessionVarObject)
' I would prefer to just use one statement
' Me = obj
' instead of delineating each private variable for each property
Me._name = obj._name
... etc.
End Sub

If you already have an instance in the session variable, there is no
reason to create a new instance. Use a factory method:

Public Shared Sub GetInstance() as SessionVarObject
Dim instance as SessionVarObject
instance = HttpContext.Current.Session(SESSION_VARIABLE);
If IsNothing(instance) Then
instance = New SessionVarObject();
saveObjectToSession(Me)
End If
Return instance
End Sub

And make the constructor private, so that the factory method is the only
way to create an instance.

 

[Don Miller]

Thanks for the pointer. But I am a little confused.

It is my ASPX VB code that will use this class instance (even if derived
from a Session Variable) and use the methods in the class to manipulate the
instance (which again has to be written back to the Session variable). It is
my understanding (I could be VERY wrong) that the methods are not part of
the instance (or is that just when an object is serialized?).

 

[=?ISO-8859-1?Q?G=F6ran_Andersson?=]

Thanks for the pointer. But I am a little confused.

It is my ASPX VB code that will use this class instance (even if derived
from a Session Variable) and use the methods in the class to manipulate the
instance (which again has to be written back to the Session variable). It is
my understanding (I could be VERY wrong) that the methods are not part of
the instance (or is that just when an object is serialized?).

The methods aren't part of the instance, they are part of the class.
That means that every instance of the class can use the methods.

When you serialize an object, you turn it into a chunk of data, and that
chunk of data isn't an object so it doesn't have any methods or
propertys or anything. When you deserialize the data it's done by
creating a new object containing the same data as the original object.
That object has access to the same methods as the original object as it
is of the same class.

 

[Don Miller]

Thanks for your explanation.

The methods aren't part of the instance, they are part of the class. That
means that every instance of the class can use the methods.

When you serialize an object, you turn it into a chunk of data, and that
chunk of data isn't an object so it doesn't have any methods or propertys
or anything. When you deserialize the data it's done by creating a new
object containing the same data as the original object. That object has
access to the same methods as the original object as it is of the same
class.