Above declaration in the global.asa file might be familiar to almost all ASP programmers.

While going through the MSDN, I was overwhelmed, by looking into the web.config file which handles all configuration for an application. The replacement for the above declaration in ASP .NET is as follows:

<configuration>
<appSettings>
<add key="DSN" value="Server=moon;database=Store;Trusted_Connection=yes" />
</appSettings>
</configuration>

Then, in your ASPX page, you should have the following statement to retrieve the value for DSN.

Dim dsn As String = ConfigurationSettings.AppSettings("DSN")

So, I started to ask the following questions to myself.

What exactly is web.config?
Does this handles only the above example?
What are the benefits of web.config?

And, following were the results for my questions, and I would like to share with you all. This is based on Beta2

Introduction

Well, web.config is a XML-based configuration file. If you see the above example, you can make sure that all the elements are based on XML standards. Obviously, we can develop a tool for modifying and editing this configuration file.

A web.config can appear in any directory on an ASP.NET Web application server. Said this, if you have a web.config file in the directory "c:\inetpub\wwwroot", then the settings specified in the web.config is applicable to all the subdirectories under wwwroot. Each sub-directory can have its own web.config file and it will overwrite the settings of the web.config file in the parent directory.

There is another file called machine.config, which provides configuration settings for the entire server. If you change the contents of any web.config file then the change will be immediately reflected in the processing of any incoming requests to the web' server. These settings are calculated only once and then cached across subsequent requests. ASP.NET automatically watches for file changes and will invalidate the cache if any of the configuration files change. (For more information on caching Click here)

The root element of a web.config file is always a <configuration> tag. The <configuration> tag contains three different types of elements: 1) configuration section handler declarations, 2) configuration section groups, and 3) configuration section settings.

Following are the list of commonly used Configuation tags, that, we be used in our web applications and will go thru them

<appSettings>

Eg: <add key="DSN" value="Server=moon;database=Store;Trusted_Connection=yes" />

<authentication>

Form based authentication can be used, if you want to use ASP .NET forms-based authentication.

If you want to allow anyonmyous users to access your website, select none.

Passpost authentication can be used, if you want the authentication to be based on Microsoft Passport authentication mode.

Use windows mode authentication, if you want to use Basic, Digest, Integrated Windows authentication (NTLM/Kerberos), or certificates

Note: If you are using Form based authentication, then you have several other options such as how the password should be encrypted, while submitting the form, if login fails, which page should be shown to the user etc.

As the AuthenTication is included in, System.Web.Configuration.AuthenticationConfigHandler while setting the authentication mode, you should code as follows

<authorization>

Allow tag provides us with three attributes, namely users, roles and verbs. We can add the list of users seperated by comma in the users attribute. Also we can specify the role in which each user belongs too. Important aspect of the attribute verb is that, we can control users depending upon the web request that the server is getting. The verb attribute provides us with four options GET, HEAD, POST and DEBUG.

Deny tag has the same attributes as the allow tag has. Other aspect of both these tags are, we can use two special symbols ? and * to specify anonymous users and "all users" respectively.

<compilation>

Attributes
debug specifies whether to compile retail binaries or debug binaries. True specifies debug binaries and False specifies Retail binaries

defaultLanguage can be used to specify the language names to use in dynamic compilation files.

use explicit attribute to turn on explicit option or to turn off. This takes either true or false, were true means explicit is enabled.

We can also do a batch compiliation by specifying the attribute bath as true. If we have batch compiliation, then we might face the timeout problem. Then we may also want to use the batchTimeout attribute to set the time for batch timeout.

numRecompilesBeforeApprestart is the next attribute. This attribute indicates the number of dynamic recompiles of resources that can occur before the application restarts. This attribute is supported at the global and application level but not at the directory level.

Strict attribute indicates the settings of the visual basic strict compile option. supports two values, TRUE and FALSE.

SubTags
Compilers tag contains many or one compiler tag, were we define new compiler options. Assemblies and Namespaces specifies ASP .NET processing directives

<customErrors>

defaultRedirect can be used to specify the URL to direct a browser, if any unexpected error occurs. The mode attribute takes three values On, Off or RemoteOnly. Remeteonly specifies that custom errors are shown only to remote clients.

The subtag <error> might be very useful in a variety of way. We can specify the error status code and ask the browser to redirect to a specific page. We should use the attribute, statusCode to specify the error status code and the redirect attribute to specify the redirect URL.

<globalization>

<identity>

<machineKey>

ValidationKey and DecryptionKey takes the default value, which is AutoGenerate. We can also specify a key and it should be length of 128 hexadecimal characters. The validation attribute can be used to specify the alogrithm to be used while encryption. Possible values are SHA1, MD5 and 3DES.