Hidden Features of ASP.NET [closed]

Question

While testing, you can have emails sent to a folder on your computer instead of an SMTP server. Put this in your web.config:

<system.net>
    <mailSettings>
        <smtp deliveryMethod="SpecifiedPickupDirectory">
            <specifiedPickupDirectory pickupDirectoryLocation="c:\Temp\" />
        </smtp>
    </mailSettings>
</system.net>

If you place a file named app_offline.htm in the root of a web application directory, ASP.NET 2.0+ will shut-down the application and stop normal processing any new incoming requests for that application, showing only the contents of the app_offline.htm file for all new requests.

This is the quickest and easiest way to display your "Site Temporarily Unavailable" notice while re-deploying (or rolling back) changes to a Production server.

Also, as pointed out by marxidad, make sure you have at least 512 bytes of content within the file so IE6 will render it correctly.

throw new HttpException(404, "Article not found");

This will be caught by ASP.NET which will return the customErrors page. Learned about this one in a recent .NET Tip of the Day Post

Here's the best one. Add this to your web.config for MUCH faster compilation. This is post 3.5SP1 via this QFE.

<compilation optimizeCompilations="true">

Quick summary: we are introducing a new optimizeCompilations switch in ASP.NET that can greatly improve the compilation speed in some scenarios. There are some catches, so read on for more details. This switch is currently available as a QFE for 3.5SP1, and will be part of VS 2010.

The ASP.NET compilation system takes a very conservative approach which causes it to wipe out any previous work that it has done any time a ‘top level’ file changes. ‘Top level’ files include anything in bin and App_Code, as well as global.asax. While this works fine for small apps, it becomes nearly unusable for very large apps. E.g. a customer was running into a case where it was taking 10 minutes to refresh a page after making any change to a ‘bin’ assembly.

To ease the pain, we added an ‘optimized’ compilation mode which takes a much less conservative approach to recompilation.

Via here: