February 2008
Intermediate to advanced
428 pages
8h 52m
English
Content preview from ASP.NET 3.5 For Dummies®
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
21.6. Some Common Error Messages and Where to Look
Runtime errors that happen often enough find their way onto Frequently Asked Question (FAQ) lists. In this section, I show you some exceptions that you're likely to encounter and provide you some guidance on resolving them.
21.6.1. System.Security.SecurityException
Your pages are running fine on your computer but fail when you post them to the Web site on the Internet. The exception complains: The application attempted to perform an operation not allowed by the security policy.
Web hosting companies usually lock the trust level of sites to medium rather than full. The following setting (at the machine-level web.config file) overrides whatever you try to set in your Web site:
<trust level="Medium" originUrl="" />
If a page or called component tries to use the file system (usually outside your Web site), Registry, event log, OLEDB data access, or restricted assemblies, the constraint throws a SecurityException that crashes the page.
Ask the Web host to review the trust level and perhaps allow an override or exception. To locate information on appropriate settings, search Microsoft's Web site for How to use medium trust in ASP.NET. If you're using a third-party component, check with the vendor whether their component requires full trust and if so, what you can do to make it work under medium trust.
21.6.2. System.NullReferenceException
People ask about this one all over the Internet: Object reference not set to an instance of an ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.