entwicklungsgedanken » Exception

Redirect from the OnException-method inside the controller with ASP.Net MVC

Eric Bartels — Thu, 16 Jul 2009 08:42:00 +0000

If your controller uses the HandleError-Attribute it handles exceptions thrown by action methods. I wanted to catch these exceptions and redirect to a custom error page. A simple RedirectToAction inside the OnException method does not work. But the ExceptionContext is all we need.

#region Error handling
protected override void OnException(ExceptionContext filterContext)
{
 // Make use of the exception later
 this.Session["ErrorException"] = filterContext.Exception;
 
 // Mark exception as handled
 filterContext.ExceptionHandled = true;
 
 // ... logging, etc
 
 // Redirect
 filterContext.Result = this.RedirectToAction("Error", "Home");
 
 base.OnException(filterContext);
}
#endregion

It stored the exception thrown inside the action onto the session. So this information is available inside my "error-action".

My custom "error-action" even allows me to distinguish between normal requests and Ajax-requests (where I use a partial-view instead of a normal view) to display a nicer error message to the end-user.

Problems with the ContentByQueryWebPart (CQWP) and its ItemXslLink-property

Eric Bartels — Tue, 08 Apr 2008 19:12:59 +0000

If you ever tried to set the ItemXslLink (which is a normal property of the ContentByQueryWebPart) you will see that sometimes this simply doesn’t work. You get an exception!

Object reference not set to an instance of an object

Why?

The CmsDataFormWebpart.MakeSiteRelativeUrl (which is called somewhere when setting this property) needs the HttpContext.Current which isn’t available when using a console application or inside an event receiver (déjà vu!).

Solution

Inside the MSDN-Forums a user named AlexUC found a good workaround.

if (null == HttpContext.Current)
{
    HttpRequest request = new HttpRequest ("", web.Url, "");
    HttpContext.Current = new HttpContext (request, new HttpResponse (new StringWriter ()));
    HttpContext.Current.Items["HttpHandlerSPWeb"] = web;
}

Perhaps this even works when one is inside an asynchronous-event inside an event receiver?! Perhaps one can redirect the user inside the ItemAdded-Method?!
I will analyze this soon….