ASP.NET Exception Handling presentation to user - asp.net

Question

I have added try catches in my site which work great. The next part in development is to set up some exception handling output. Obviously I don't want the site to crumble when an error occurs and I don't want a horrible error screen. So, somewhere in the middle would be nice.
I was thinking to have an exception handler user control in the main master page which wil output a nice little message when something goes wrong.
What would be the best way to pass the exception to this user control? I was thinking of using a session variable.
Does anyone have a solution to this problem?
Thanks

Answer 1

This is easier than you're making it. Create a page called error.aspx (or whatever you want to call it), and turn the CustomErrors on in the web.config.
<configuration>
<system.web>
<customErrors defaultRedirect="errors.aspx"
mode="On">
</customErrors>
</system.web>
</configuration>
There is a lot of configurability to handle different http errors or random exceptions. If you want, you can dump the exception message (or the exception itself) into the session or use the HttpServerUtility.GetLastError (documentation)and then output any number of different messages on the error page. This will even catch exceptions that you DON'T catch.
CustomErrors Documentation
Edit:
#Icarus indicates that OP is looking for a solution by which the page continues to render and output while only showing an error message within the page, so I'll provide an answer to that as well.
There are a few ways I've handled this in the past. For very complex pages where the behavior requested is fatal (the page result can't be known), I've always deferred to an error page as I mentioned above that includes major master elements. So the menu, header, etc are all still there, but the notification of cataclysm is evident.
The behavior you seem to be looking for is something I would use less out of a need to report exceptions than to report general messages. My preference is to have a user control that has a public bindable property that a message can be injected into. Such as (forgive the VB, I can't seem to find my C# version):
<BrowsableAttribute(True), Bindable(False), Category("Misc"), _
Description("Gets or sets the NavigateUrl property for the link to start a new request.")> _
Public Property MyImportantMessage() As String
Get
Return _myImportantMessage
End Get
Set(ByVal value As String)
_myImportantMessage= value
End Set
End Property
Then the output could be any string message you like or you could program in a number of presets, fetch from resources, whatever. As to how to get it in there, we have taken the MasterPage route. We have a method in our master pages which assigns such a property in the user control directly. In order for this method to be callable, each page that uses the master page has to include the VirtualPath property, otherwise the method will not be available at compile time.
<%# MasterType
VirtualPath="~/MasterPage.master" %>
This then allows the Master property to be called from within the page itself to call this property:
'Keeping the VB theme
Me.Master.SetImportantMessage(message)
Keep in mind that Me.Master from within the page is not the same as Page.Master. So your exception will either need to bubble up to the actual page or the page reference itself will have to be sent down to your usercontrols as a property.

Answer 2

If you're wanting to provide an error for a handled exception, it's really as simple as populating a label with some sort of a notice that the application had a problem processing a request. You would do this within the "catch" part of the statement. I've even gone as far as presenting different messages depending on the role of the user. For instance if an admin generates an error you could actually output the actual exception message, but if someone in a lesser role generates it it would show them a more generic error and send the admin group a message/email.
try
{
//your code here
}
catch (Exception ex)
{
if (Role!="Admin")
{
Label1.Text = "There was an error, the administrator has been notified."
}
else
{
Label1.Text = "Error: " + ex.Message + ": " + ex.StackTrace; //you could add further here if you want to look for an inner exception.
}
}