how to use an external configuration file with WPF? - wpf

Question

i would like to set up an external configuration file that I can store in a directory for my WPF app, not necessarily the directory of my exe when I create my program either.
I created an App.Config file and added System.Configuration to my assembly. My App.Config has:
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<appSettings file="sd.config">
<add key="username" value="joesmith" />
</appSettings>
</configuration>
and my sd.config (external file) which is in the root of my project for now, has
<?xml version="1.0"?>
<appSettings>
<add key="username1" value="janedoe" />
</appSettings>
in my MainWindow cs class I used
string username = ConfigurationManager.AppSettings.Get("username1");
which returns a null string. when i just retrieve the username field from App.Config it works. What did i miss? Thanks so much!

Answer 1

See the documentation on ConfigurationManager:
The AppSettings property:
Gets the AppSettingsSection data for the current application's default
configuration.
You need to do a little extra work to get data that isn't in your application's default configuration file.
Instead of using the file= attribute, add a key to your <appSettings> that defines the location of the secondary config file, like so:
<add key="configFile" value="sd.config"/>
Then, in order to use ConfigurationManager to pull settings from the secondary config file, you need to use its OpenMappedExeConfiguration method, which should look a little something like this:
var map = new ExeConfigurationFileMap();
map.ExeConfigFilename = Path.Combine(
AppDomain.CurrentDomain.SetupInformation.ApplicationBase,
ConfigurationManager.AppSettings["configFile"]
);
//Once you have a Configuration reference to the secondary config file,
//you can access its appSettings collection:
var config = ConfigurationManager.OpenMappedExeConfiguration(map, ConfigurationUserLevel.None);
var userName1 = config.AppSettings["username1"];
That code might not be dead-on for your example, but hopefully it gets you on the right track!