I have an old custom webcontrol worked fine for years on VS 2005. When I edited a ASP.NET 2.0 web site project with VS 2008, tried to drag the .NET 2.0 webcontrol from toolbox to the web page, I got this exception in IDE.
"Session state can only be used when enableSessionState is set to true, either in a configuration file or in the Page directive. Please also make sure that System.Web.SessionStateModule or a custom session state module is included in the <configuration>\<system.web>\<httpModules> section in the application configuration."
Search for this issue via Google, most of the discussions focus on session not enabled or WSS issue. I am very sure the enableSessionState is enabled and no WSS issue in my web site. Will it be design time session issue?
I reviewed my code and found this:
protected override void OnInit(EventArgs e)
//Generate a unique key
//Store some variable to session
Yeah, I use Session object in OnInit, maybe it's the cause. So the above code was modified as
Now my custom webconrol get back again in VS2008, case closed.
When Page.Session object is used during design time, VS2005 will ignore it, but VS2008 will throw an "session can not be used..." exception and cause a error desgin time display.