Getting values out of session in ASP.NET can be a bit of a pain for two reasons:
- You have to remember what you named the value when you put it in
- You have to type cast the value, as session stores it in an Object
One nice way to handle this is to build a wrapper class to handle getting values into and out of session. And an even nicer way is to use generic methods in your wrapper class.
Here’s how I implement this in my projects. First, I have a class called SessionBase that contains two shared Generic methods, LoadValue and RetrieveValue:
Public Class SessionBase
Public Shared Function RetrieveValue(Of T)(ByVal keyName As String) As T
If HttpContext.Current.Session(keyName) IsNot Nothing Then
Return DirectCast(HttpContext.Current.Session(keyName), T)
Public Shared Sub LoadValue(Of T)(ByVal keyName As String, ByVal value As T)
HttpContext.Current.Session(keyName) = value
The beauty of these methods is that they can handle any data type – I don’t have to have separate methods for integers, collections, custom types, etc. It’s all handled here in this generic and reusable class (I usually keep it in a .dll along with other base classes, and add a reference to it in my project). I use DirectCast rather than CType in my retrieve method because it is supposed to have less of a performance penalty.
Then, in my project, I create a class called sess that inherits the base class (because the base class contains shared methods, it doesn’t really need to be inherited, but I prefer to do it this way so there is less typing – I can type sess.LoadValue instead of TKS.SessionBase.LoadValue). In the project-specific class, I create constants for the session key names, and shared properties to load and retrieve values from session:
Public Class sess
Private Const cProjID As String = "ProjID"
Private Const cProjName As String = "ProjName"
Public Shared Property ProjID() As Integer
Return sess.RetrieveValue(Of Integer)(cProjID)
Set(ByVal value As Integer)
sess.LoadValue(of Integer)(cProjID, value)
Public Shared Property ProjName() As String
Return sess.RetrieveValue(Of String)(cProjName)
Set(ByVal value As String)
sess.LoadValue(Of String)(cProjName, value)
Note how the generic methods are made specific at this point – Integer for ProjID, String for ProjName.
Now in my project, I can use the sess properties to easily access the session object:
Protected Sub btnLoad_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnLoad.Click
sess.ProjID = Integer.Parse(Me.txtProjectID.Text)
sess.ProjName = Me.txtProjectName.Text
Protected Sub btnRetrieve_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles btnRetrieve.Click
Me.txtProjectID.Text = sess.ProjID.ToString
Me.txtProjectName.Text = sess.ProjName