Problem loading assembly via Reflection and accessing configuration

Question

I'm trying to load a .NET assembly with Reflection (using the Assembly.LoadFrom method), and instantiate some types within this assembly.

This all seems to work fine, but one type I'm trying to instantiate accesses the assembly's configuration within its type initializer: it does ConfigurationManager.GetSection(sectionName). The assembly is then throwing an exception because the configuration section cannot be found.

The config file for the assembly I'm loading is in the same directory, and has the standard name (i.e. AssemblyName.dll.config), and the config definitely has the section being requested. Why can't the configuration section be found? Is there something extra I need to do when loading the assembly?

Darin Dimitrov · Accepted Answer · 2010-07-28 09:50:22Z

6

Because the configuration file being read is the configuration file of the hosting executable. So for example if you are running you code from Foo.exe your config file should be named Foo.exe.config. The AssemblyName.dll.config is never used. If you are running this in a web site then you should use web.config.

You could try using the OpenMappedExeConfiguration method:

var configFileMap = new ExeConfigurationFileMap();
configFileMap.ExeConfigFilename = "AssemblyName.dll.config";
var section = ConfigurationManager.OpenMappedExeConfiguration(configFileMap, ConfigurationUserLevel.None).GetSection(sectionName);

edited Jul 28, 2010 at 9:50

answered Jul 28, 2010 at 9:41

Darin Dimitrov

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2 Comments

Graham Clark Over a year ago

Ok, that makes sense. Is there any (nice) way I can use the config from the assembly I'm loading? Maybe merge it into my application's config somehow..?

Darin Dimitrov Over a year ago

Yes, you could use the OpenMappedExeConfiguration method to specify the location of the config file you would like to open and read values from.

Jen Grant · Accepted Answer · 2011-02-04 00:47:52Z

The following maps the file and then opens it as a System.Configuration Variable:

string FilePath = System.Reflection.Assembly.GetAssembly(typeof(EncryptDecryptViewModel)).Location 
FilePath += @".config";                
var ConfigFileMap = new ExeConfigurationFileMap();
ConfigFileMap.ExeConfigFilename = FilePath;
Configuration LocalConfigurationManager = ConfigurationManager.OpenMappedExeConfiguration(ConfigFileMap, ConfigurationUserLevel.None);

You can now retrieve values from the assemblies configuration file much like you would through the configuration manager, however you must be a little bit more explicit in your requests.

When using System.Configuration.ConfigurationManager, the following would be valid and return a value:

string s = System.Configuration.ConfigurationManager.AppSettings["SomeSetting"];

However when using the Configuration variable LocalConfigurationManager (from the code above) a call like the normal ConfigurationManager call such as:

string s = LocalConfigurationManager.AppSettings["ConfigurationSections"];

You would get the following error when you attempt to run the code:

'System.Configuration.ConfigurationElement.this[System.Configuration.ConfigurationProperty]' is inaccessible due to its protection level

This is because in the ConfigurationManager the AppSettings property is a NameValueCollection. In the Configuration variable, AppSettings is actually a System.Configuration.AppSettingsSection which contains a property called Settings that is a KeyValueConfigurationCollection so to access the property the call would look like this:

string s = LocalConfigurationManager.AppSettings.Settings["SomeSetting"].Value;

For the Connection Strings Secion, the following syntax would be used

string ConnectionString =  LocalConfigurationManager.ConnectionStrings.ConnectionStrings["connectionStringName"].ConnectionString;

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