Programmatically Changing Session State Behavior in ASP.NET 4.0

• Download ASP.NET 4.0 State Management – Deep Dive PPT

Session is one of the most important state managements in ASP.NET. We can enable or disable session state either in web.config or using @Page directive’s EnableSessionState attributes. But there was no provision to change the session state at runtime till date in ASP.NET. But using ASP.NET 4.0, we can change the session state programmatically. The .NET 4.0 Framework adds a new method SetSessionStateBehavior to the HttpContext class for ASP.NET. This method required SessionStatebehavior value to set the current session mode. To call SetSessionStateBehavior, simply create a new HttpModule by implementing IHttModule and hook the BeginRequest event. Most importantly, you can only use the SetSessionStateBehavior until the AcquireRequestState event is fired, because AcquireRequestState occurs when ASP.NET acquires the current state that is associated with the current request.

While calling SetSessionStatebehavior, you can pass the following values as SessionStatebehavior:

• Default: This is the default setting which means everything works as before
• Disabled: Turned of Session State for Current Request
• ReadOnly: Read only access to Session State
• Required: Enabled session state for both Read and Write Access

Let’s have a look into a quick example where I will show how you can change the session state based on the different member types of your web site. Let’s say you have 3 different types of members (Gold, Silver and Platinum) and for Platinum member you want to maintain the session for some specific pages not for other. To start with this first, create an new HTTP Module by implementing IHttpModule Interface.

using System;
using System.Web;

/// <summary>
/// Summary description for SessionModule
/// </summary>
public class SessionModule : IHttpModule
{
    /// <summary>
    /// Disposes of the resources (other than memory) used by the module 
    /// that implements <see cref="T:System.Web.IHttpModule"/>.
    /// </summary>
    public void Dispose() { }

    /// <summary>
    /// Initializes a module and prepares it to handle requests.
    /// </summary>
    /// <param name="context">An <see cref="T:System.Web.HttpApplication"/> 
    /// that provides access to the methods, properties, and events common 
    /// to all application objects within an ASP.NET application</param>
    public void Init(HttpApplication context)
    {
        context.BeginRequest += new EventHandler(context_BeginRequest);
    }

    /// <summary>
    /// Handles the BeginRequest event of the context control.
    /// </summary>
    /// <param name="sender">The source of the event.</param>
    /// <param name="e">The <see cref="System.EventArgs"/> 
    /// instance containing the event data.</param>
    void context_BeginRequest(object sender, EventArgs e)
    {
        HttpContext currentContext = (sender as HttpApplication).Context;    

        if (!string.IsNullOrEmpty(currentContext.Request.QueryString["memberType"]))
        {
            if (currentContext.Request.QueryString["memberType"].ToString().Equals
		("Platinum"))
            {
                currentContext.SetSessionStateBehavior
		(System.Web.SessionState.SessionStateBehavior.Required);
            }
        }
    }
}

From the above code block, you can see, based on the member type which is nothing but a query string, I am changing the session state.

Now, if you have Session disabled in @Page Directive, it will automatically override the settings.

Once you are done with implementation of HTTP Module, you have to configure web.config for the same.

Again, you have to make sure that you can only use SetSessionStateBehavior until the AcquireRequestState event is fired.

And, not only with Query string, you can enable or disable session state based on the different page as shown below:

To know more about ASP.NET 4.0 State management, you can read my Session notes on Microsoft Community Tech Days – Hyderabad

You will get the complete demo application on runtime session state change from the download at the top of this article.

Hope this will help you!

Cheers !
AJ

Filed under: ASP.NET 4.0, General, Visual Studio 2010