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ASP.NET Web.config

The ASP.NET Web.config file is used to define the configuration settings for an ASP.NET application. 
ASP.NET and the .NET Framework use .config files to define all configuration options. 
The .config files, including the ASP.NET Web.config file, are XML files. 

Server-wide configuration settings for the .NET Framework are defined in a file called Machine.config. 
The settings in the Machine.config file can be changed and those settings affect all .NET applications on the server. 

Different ASP.NET applications might need different application settings, that’s why defining those settings in the Machine.config file, is usually not practical. 
The solution for this problem is the ASP.NET Web.config file.

The ASP.NET application configuration settings can be changed by creating a file called Web.config and saving it in the root folder of the application. 
But what if the Machine.config file defines different settings than the ones defined in your Web.config file? 
The good news is that the settings in the Web.config file override the settings in the Machine.config file.

This is how the minimal Web.config file should look like:

<?xml version="1.0" encoding="utf-8" ?>

The first line of the Web.config file is the same as the first line for any .config file and specifies that this is an XML document with utf-8 character encoding type.

There are 2 important characteristics of the Web.config file. 
The first one is that if you change your Web.config file, you don’t need to re-compile your ASP.NET application.
The second one is that the Web.config file cannot be viewed in directly in a browser.

How can we use the ASP.NET Web.config file?

<appSettings> Web.config section

The ASP.NET Web.config file is a perfect place to store your ASP.NET application configuration settings. 
For example you can store your database connection string in Web.config file and access them easily from your ASP.NET application. 
Why would you want to keep your database connection strings in the Web.config file? The reason is simple – easier maintenance and deployment. 
Imagine that you have a huge ASP.NET application, with several hundreds pages connecting and interacting with a database. 
If all those pages have the database connection string hard-coded in them, it will be a nightmare to change all those strings in case you are changing database servers. 
Using the Web.config file to store the database connection strings will allow you to change the connection string only once, and you don’t have to even re-compile the whole application. 
Of course you can keep any application wide settings in your Web.config file, not only database connection strings.

The ASP.NET Web.config file can control many more settings like Session State, Tracing and Authentication & Authorization for example.
Sean Marcellus
There are 10 kinds of people e in this world, those who understand binary and those who don’t.