Is reading app.config expensive?

Question

No question I am yet to be hit by any read speed bottleneck. I am asking to know; if reading app.config frequently is a bad programming choice. I have known of database operations getting expensive.

In my case I am not reading my own application's app.config, but of another project's, like this:

private string GetAppConfigValue(string key)
{
    ExeConfigurationFileMap fileMap = new ExeConfigurationFileMap();
    fileMap.ExeConfigFilename = GetConfigFilePath();
    Configuration appConfig = ConfigurationManager.OpenMappedExeConfiguration(fileMap, ConfigurationUserLevel.None);
    return appConfig.AppSettings.Settings[key].Value;
}

Scenario: I have a manager class (and only one such class) where I have to read few values (3 to 4) from a config file specified by a physical path, but many times. Need I have few member variables to store the values from app.config file? What would be the best approach. Thanks.

Answer 1

I'm sure that all configuration files(web.config or app.config) are cached by default, so you don't need to create a static class that holds all values or be afraid that the files are accessed permanently.

Here is some reading:

• Web.Config is Cached
• ConfigurationManager.RefreshSection Method
• Application Configuration Files Explained
• ASP.NET Configuration Overview

Regarding to your requirement to access another application's config file:

MSDN: "These methods(note: for client applications: ConfigurationManager.GetSection) provide access to the cached configuration values for the current application, which has better performance than the Configuration class."

In other words: Yes, you should cache it when it's not your own app's config file.