is it a good idea to create an enum for the key names of session values?

Question

instead of doing

 session(\"myvar1\") = something
 session(\"myvar2\") = something
 session(\"myvar3\") = something
 session(\"myvar4\") = something

Answer 1

Instead of using constants for the session keys, I'm using my own type-safe session object, which looks like this (sorry this is in C#, see below for a VB version):

public class MySession
{
  // Private constructor (use MySession.Current to access the current instance).
  private MySession() {}

  // Gets the current session.
  public static MySession Current
  {
    get
    {
      MySession session = HttpContext.Current.Session["__MySession__"] as MySession;
      if (session == null)
      {
        session = new MySession();
        HttpContext.Current.Session["__MySession__"] = session;
      }
      return session;
    }
  }

  // My session data goes here:
  public string MyString { get; set; };
  public bool MyFlag { get; set; };
  public int MyNumber { get; set; };
}

Whenever I need to read/write something to/from the session, I can use my typesafe session object like this:

string s = MySession.Current.MyString;
s = "new value";
MySession.Current.MyString = s;

This solution results in several advantages:

• I have a typesafe Session (no more type-casts)
• I can document all session based data (by commenting the public properties in MySession)
• When adding a new element to the session, I don't have to search the solution to check if the same session-key was already used somewhere else.

Update: Here's a VB version (automatically converted from the C# version). Sorry, but I don't know VB and so I didn't know how to write the properties in VB:

Public Class MySession
    ' Private constructor (use MySession.Current to access the current instance).
    Private Sub New()
    End Sub

    ' Gets the current session.
    Public Shared ReadOnly Property Current() As MySession
        Get
            Dim session As MySession = TryCast(HttpContext.Current.Session("__MySession__"), MySession)
            If session = Nothing Then
                session = New MySession()
                HttpContext.Current.Session("__MySession__") = session
            End If
            Return session
        End Get
    End Property

    ' My session data goes here:
    Public MyString As String
    Public MyFlag As Boolean
    Public MyNumber As Integer
End Class