Multiple web configs in .Net

Web.config exposes an element that can be used as a place to store application settings like connection strings, file paths, etc. Using the web.config is an ideal method of creating a robust application that can quickly adapt to changes in its environment. For instance, if the connection string is stored in web.config and is being called from the web-pages from there, then changes in the connection string will have to be made in web.config only. Otherwise, the user would have to go to each page individually and update the connection string.

Let us look at a basic web.config which holds our connection string.



























To read the connection setting from the Config file, you have to use a single line of code:



System.Configuration.ConfigurationManager.AppSettings("ConnectionInfo")


Multiple Config Files

The appSettings element can contain a file attribute that points to an external file. I will change my web.config file to look like the following:























Next, we can create the external file "externalSettings.config" and add an appSettings section with our connection information and any other settings that we want to use.

If the external file is present, ASP.Net combines the appSettings values from web.config with those in the external file. If a key/value exists in both files, then ASP.Net will use the setting from the external file.

This feature is useful when one keeps user-specific or environment-specific settings in the external file. It is better to design web.config to contain those settings that are global, while each user setting is contained in an external file. This approach makes it easier to move around global web.config changes.

One caution to this approach is that ASP.Net runtime does not detect when the external file changes. Thus to launch a new version of the application with all changes in effect, one will need to make changes to the web.config itself.
And all things must come to an end

The main emphasis in this article was on Application Settings - Multiple Config Usage. I hope you found this article interesting and informative. I am open for suggestions and remarks, both negative and positive. Feel free to contact me at
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