Web.config files in .NET 3.0 and 3.5
Over the last few releases, the web.config files within new ASP.NET projects have steadily increased in size. For example: the default web.config file that is added to a new web project in Visual Studio 2008 SP1 is now some 126 lines long, and contains everything from tag definitions to definitions of handlers and modules to be included in the ASP.NET HTTP pipeline.
This increase in size is because .NET 3.0 and .NET 3.5 use the same CLR and machine.config configuration file as those shipped with .NET 2.0 – and simply add and update assemblies in the framework when they are installed. To avoid the risk of us accidentally overwriting customized settings within the original 2.0 machine.config on the machine, we didn’t register the tag definitions, handlers and modules that shipped with the new ASP.NET functionality that came with the .NET 3.0 and .NET 3.5 versions. Instead, we defaulted to having new projects register these settings within the application’s local web.config file instead. This was safer – but caused the web.config files to increase and become more complicated and harder to read.
Web.config files in .NET 4
.NET 4 includes a new version of the CLR, and a new .NET 4 specific machine.config file (which is installed side-by-side with the one used by .NET 2, .NET 3 and .NET 3.5).
The new .NET 4 machine.config file now automatically registers all of the ASP.NET tag sections, handlers and modules that we’ve added over the years, including the functionality for:
ASP.NET AJAX
ASP.NET Dynamic Data
ASP.NET Routing (which can now be used for both ASP.NET WebForms and ASP.NET MVC)
ASP.NET Chart Control (which now ships built-into ASP.NET V4)
What this means is that when you create a new “Empty ASP.NET application” project in VS 2010, you’ll find that the new default application-level web.config file is now clean and simple:
