App.config and F# Interactive not working

Question

As I'm polishing my little pet project, I'm trying to store all the constant strings in my app.config file (Keys, XpathExpressions etc). When I run the compiled exe this works great. In the Interactive Shell this isn't the case.

I tried to copy the .config file from my bin/Release directory to the obj/Debug & obj/Release dirs, but the Call to ConfigurationManager.AppSettings.Item("key") always returns null.

Any suggestions how to fix this?

With best regards

Answer 1

F# Interactive can work with executables that rely on app.config files.

The way to do this is to have an .fs file in your project that loads your .config conditional on the COMPILED define so:

let GetMyConfig() =
  let config  = 
    #if COMPILED 
      ConfigurationManager.GetSection("MyConfig") :?> MyConfig
    #else                        
      let path = __SOURCE_DIRECTORY__ + "/app.config"
      let fileMap = ConfigurationFileMap(path) 
      let config = ConfigurationManager.OpenMappedMachineConfiguration(fileMap) 
      config.GetSection("MyConfig") :?> MyConfig
    #endif

then in your script file reference the executable and #load the .fs file so:

#I "../Build/Path

#r "ConfiguredApp.exe"

#load "MyConfig.fs"

On executing these three lines you will see a message similar to the following in the FSI window:

[Loading C:\Svn\trunk\Source\ConfiguredApp\MyConfig.fs]

Binding session to 'C:\Svn\Qar\trunk\Build\Path\ConfiguredApp.exe'...

Notice that you're actually referencing the app.config when in FSI (rather than the generated .exe.config.)

Best of luck...