Using different .config file in .NET application

In .NET world executable files use, by default, a configuration file with a special name. Microsoft has implemented the following pattern: executable: program.exe and a corresponding configuration file program.exe.config. In many scenarios this pattern fits well, but there are some cases when something else is necessary. In my situation common configuration file was desirable! One configuration file with shared app settings, configuration strings, etc.

First solution I found was sharing AppSettings section between configuration files. This can be easily achieved by adding a file attribute in the appSettings tag. Like this:

<appSettings file="commonSettings.config">

But this doesn’t solve the problem with connection strings and custom sections… damn…

The solution that I end up with is:

AppDomain.CurrentDomain.SetData("APP_CONFIG_FILE", @"commonConfig.config");

FieldInfo fiInit = typeof(ConfigurationManager).GetField("s_initState", BindingFlags.NonPublic ' BindingFlags.Static);

if (fiInit != null)
{
fiInit.SetValue(null, null);
}

ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None);

The AppDomain.CurrentDomain.SetData() method changes properties for current domain. So I simply change the APP_CONFIG_FILE property value to point to another config file. The rest of the code is necessary to re-read the configuration. With this solution I am able to force .NET to use one configuration file between multiple executables.