How to: Read application settings

This article shows you how to add a simple setting to an App.config file in a .NET Framework app, and then read the value programmatically. Instead of just reading a single value, you can read an entire section or the entire file. For more examples and information, see the ConfigurationManager docs.

Add the App.config file

Visual Studio makes it easy to add an App.config file to your project. After creating a .NET Framework project, right-click on your project in Solution Explorer and choose Add > New Item. Choose the Application Configuration File item and then select Add.

Add a setting

Open the App.config file and add the following XML within the <configuration> element.

  <appSettings>
    <add key="occupation" value="dentist"/>
  </appSettings>

Access the setting programmatically

To access the setting's value in your code, get the value by indexing into the AppSettings property. The AppSettings property makes it easy to obtain data from the <appSettings> element of your configuration file.

string occupation = ConfigurationManager.AppSettings["occupation"];

Configuration for libraries

While it's straightforward to use configuration files for executable apps, it's a little more complicated for class libraries. Class libraries can access configuration settings in the same way as executable apps, however, the configuration settings must exist in the client app's App.config file. Even if you distribute an App.config file alongside your library's assembly file, the library code will not read the file. Alternatively, consider the following ways to use configuration settings in a class library:

• Obtain the configuration settings in the client app and pass them to the class you're instantiating from the class library.
• Implement a custom section type that extends the ConfigurationSection class. Keep a separate configuration file for your class library, and then reference the library's configuration file from the client app's configuration file. For more information, see How to: Create Custom Configuration Sections Using ConfigurationSection.

See also

• System.Configuration.ConfigurationManager