Environment Variable in app.config appSettings file attribute

Question

How do I point my app.config appSettings' external file to point to a path using an environment variable? The below is not recognized:

<appSettings file="%AppData%\MyApp\MySettingsFile.config" />

However, absolute paths are recognized, even though they are not within the hierarchy of the output path of the assembly, such as:

<appSettings file="C:\MyApp\MySettingsFile.config" />

Answer 1

You can do it as below:

If your changes in app.config as below:

<appSettings file="%AppData%\MyApp\MySettingsFile.config" />

then in .cs file, just expand the environment variable using Environment.ExpandEnvironmentVariables as below:

var pathConfig = ConfigurationManager.AppSettings["file"];
var expandedPath = Environment.ExpandEnvironmentVariables(pathConfig);

expandedPath will have the expanded path.

Answer 2

"The path specified is relative to the main configuration file. For a Windows Forms application, this would be the binary folder (such as /bin/debug), not the location of the application configuration file. For Web Forms applications, the path is relative to the application root, where the web.config file is located."

https://msdn.microsoft.com/en-us/library/aa903313(v=vs.71).aspx

I'm guessing your scenario works when calling the full path because your MySettingsFile.config is still within your application heirarchy.