How to replace "Error. An error occurred while processing your request."

Question

In my Web.config I have.

<customErrors mode="On" defaultRedirect="~/Errors/Unknown">
  <error statusCode="403" redirect="~/Errors/Forbidden"></error>
  <error statusCode="404" redirect="~/Errors/NotFound"></error>
</customErrors>

It works fine if I try to open a page that doesn't exist. (It redirects to my custom error page: ErrorsController.NotFound). When an unhandled exception occurs (in this case in LINQ Signle(...)). It doesn't go to ~/Errors/Unknown, but displays default message:

Error. An error occurred while processing your request.

How replace it with my ErrorsController.Unknown ?

Solution

Thanks to this question I figured out how to do this. The code below is almost the same as the accepted answer's. The modification handles no HttpExceptions too.

Steps to make it work:

1. customErrors element in web.config will now be ignored

2. Paste the method below to your Global.axax.

   protected void Application_Error(object sender, EventArgs e)
   {
       Exception exception = Server.GetLastError();
       Response.Clear();
   
       var httpException = exception as HttpException;
   
       if (httpException != null)
       {
           string action;
   
           switch (httpException.GetHttpCode())
           {
               case 404:
                   // page not found
                   action = "NotFound";
                   break;
               case 403:
                   // forbidden
                   action = "Forbidden";
                   break;
               case 500:
                   // server error
                   action = "HttpError500";
                   break;
               default:
                   action = "Unknown";
                   break;
           }
   
           // clear error on server
           Server.ClearError();
   
           Response.Redirect(String.Format("~/Errors/{0}", action));
       }else
       {
           // this is my modification, which handles any type of an exception.
           Response.Redirect(String.Format("~/Errors/Unknown")); 
       }
   }