Sitefinity - Remove Session after Logout - session

Question

I am trying to clear a HttpContext.Current.Session after User logs out of a Sitefinity page.
I saw in this link that you can check the Request.Url but I'm not exactly sure what the implementation is.
This is my current attempt:
protected void Application_AuthenticateRequest(object sender, EventArgs e)
{
if (((System.Web.HttpApplication)(sender)).Request.Url.ToString() == HttpContext.Current.Server.MapPath("~/Sitefinity/Login/DoLogout"))
{
if (HttpContext.Current.Session["Cart"] != null) HttpContext.Current.Session.Remove("Cart");
HttpContext.Current.Session["Cart"] = new List<IQuoteResult>();
}
}
Please let me know if you have any tips or suggestions, or if I'm completely wrong with my logic.
Thanks in advance.
UPDATE:
protected void Application_PostAcquireRequestState(object sender, EventArgs e)
{
if (((HttpApplication)(sender)).Request.Url.ToString().Contains("sign_out=true"))
{
if (HttpContext.Current.Session["Cart"] != null)
{
HttpContext.Current.Session.Remove("Cart");
HttpContext.Current.Session["Cart"] = new List<IQuoteResult>();
}
}
}
This is my next attempt at completing the same task but I keep receiving a NullReferenceException...
Note: I've also tried this method in the Application_AcquireRequestState method.
Here is the stack:
[NullReferenceException: Object reference not set to an instance of an object.]
SitefinityWebApp.Global1.Application_PostAcquireRequestState(Object sender, EventArgs e) +137
System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +91
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +164

Answer 1

This ended up being my solution:
public bool IsUserLoggingOut { get; set; }
protected void Application_PostAcquireRequestState(object sender, EventArgs e)
{
if (((HttpApplication)(sender)).Request.Url.ToString().Contains("/Sitefinity/SignOut"))
{
IsUserLoggingOut = true;
}
if (IsUserLoggingOut && SystemManager.CurrentHttpContext.Session != null)
{
SystemManager.CurrentHttpContext.Session.Remove("Quote");
IsUserLoggingOut = false;
}
}
Looks like Sitefinity has its own SystemManager to access the http context. It worked perfectly.

Answer 2

That's pretty close to how I would do it. The only change I would make is change your url comparison logic to be something like:
if (((System.Web.HttpApplication)(sender)).Request.Url.ToString().EndsWith("/Sitefinity/Login/DoLogout"))
Or potentially use .Contains() instead of EndsWith() -- not sure if there are any query-string parameters or trailing slashes added on the DoLogout action.
This is because Request.Url returns a URL (ex. https://stackoverflow.com/whatever) whereas Server.MapPath() returns a local path (ex. C:\inetpub\wwwroot\whatever), so you wouldn't be comparing apples to apples if you're comparing the two.
Edit:
Something like this should work, just adding a check to see if the session is null
protected void Application_PostAcquireRequestState(object sender, EventArgs e)
{
if (((HttpApplication)(sender)).Request.Url.ToString().Contains("sign_out=true"))
{
if (HttpContext.Current.Session != null && HttpContext.Current.Session["Cart"] != null)
{
HttpContext.Current.Session.Remove("Cart");
HttpContext.Current.Session["Cart"] = new List<IQuoteResult>();
}
}
}