What is custom tag in web.config file?

In the context of the web.config file, the term "custom tag" is not a standard term or concept. It could refer to a custom section or a custom element that you define in the web.config file to store application-specific configuration settings.

Custom sections or elements allow you to extend the default configuration structure of the web.config file to accommodate specific requirements of your application. You can define your own XML elements or sections with custom names and structures, and then access and utilize those custom settings within your application.

For example, let's say you have an application that requires some specific settings related to a third-party library or a custom module. You can define a custom section in the web.config file to store those settings. Here's an example:

<configuration>
    <configSections>
        <section name="MyCustomSettings" type="MyApp.CustomSettingsSection, MyApp" />
    </configSections>
    <MyCustomSettings>
        <Setting1>Value1</Setting1>
        <Setting2>Value2</Setting2>
    </MyCustomSettings>
    <!-- Other sections and elements go here -->
</configuration>

In the above example, the <configSections> element is used to register the custom section called "MyCustomSettings". It specifies the section name and the corresponding type that implements the custom section (e.g., CustomSettingsSection class in the MyApp namespace). The custom settings are then defined within the <MyCustomSettings> element.

After defining the custom section, you can access and retrieve the custom settings programmatically within your application by using the ConfigurationManager.GetSection method.

Using custom tags or sections in the web.config file allows you to organize and manage application-specific settings in a structured manner, providing flexibility for customization and extension of the configuration.