How do I get the values from a ConfigSection defined as NameValueSectionHandler when using ConfigurationManager.OpenMappedExeConfiguration

Question

Getting the values from a config file that uses a section defined by System.Configuration.NameValueSectionHandler is easy when you're using the current config file for the application.

Example Config file.

<configuration>
  <configSections>
    <section name="MyParams" type="System.Configuration.NameValueSectionHandler" />
  </configSections>

  <MyParams>
    <add key="FirstParam" value="One"/>
    <add key="SecondParam" value="Two"/>
  </MyParams>
</configuration>

Example Code that easily reads it.

NameValueCollection myParamsCollection =
   ConfigurationManager.GetSection("MyParams") as NameValueCollection;

This is the code that doesn't work.

NameValueCollection collection =
  ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None)
  .GetSection("MyParams") as NameValueCollection;

That fails with the following error on compile.

Cannot convert type 'System.Configuration.ConfigurationSection' to 'System.Collections.Specialized.NameValueCollection' via a reference conversion, boxing conversion, unboxing conversion, wrapping conversion, or null type conversion.

ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None) returns a System.Configuration.Configuration, and Configuration.GetSection returns ConfigurationSection.

ConfigurationManager.GetSection returns object.

So, how do I get back my NameValueCollection when I have to use OpenExeConfiguration?

Answer 1

I ran across my own answer from two years ago.

NameValueSectionHandler - can i use this section type for writing back to the application config file?

This is my approach to solve my current issue.

ExeConfigurationFileMap configFileMap = new ExeConfigurationFileMap() { 
   ExeConfigFilename = "path to config here" 
    };

Configuration config = ConfigurationManager.OpenMappedExeConfiguration(
   configFileMap, ConfigurationUserLevel.None);

ConfigurationSection myParamsSection = config.GetSection("MyParams");

string myParamsSectionRawXml = myParamsSection .SectionInformation.GetRawXml();
XmlDocument sectionXmlDoc = new XmlDocument();
sectionXmlDoc.Load(new StringReader(myParamsSectionRawXml ));
NameValueSectionHandler handler = new NameValueSectionHandler();

NameValueCollection handlerCreatedCollection = 
   handler.Create(null, null, sectionXmlDoc.DocumentElement) as NameValueCollection;

Console.WriteLine(handlerCreatedCollection.Count);

A method that works with any of the legacy IConfigurationSectionHandler types NameValueSectionHandler, DictionarySectionHandler, SingleTagSectionHandler.

public static object GetConfigurationValues(string configFileName, string sectionName)
{
    ExeConfigurationFileMap configFileMap = new ExeConfigurationFileMap() { ExeConfigFilename = configFileName };
    Configuration config = ConfigurationManager.OpenMappedExeConfiguration(configFileMap, ConfigurationUserLevel.None);
    ConfigurationSection section = config.GetSection(sectionName);
    string xml = section.SectionInformation.GetRawXml();
    XmlDocument doc = new XmlDocument();
    doc.Load(XmlReader.Create(new StringReader(xml)));
    string type = section.SectionInformation.Type;
    string assemblyName = typeof(IConfigurationSectionHandler).Assembly.GetName().FullName;
    ObjectHandle configSectionHandlerHandle = Activator.CreateInstance(assemblyName, section.SectionInformation.Type);
    if (configSectionHandlerHandle != null)
    {
        IConfigurationSectionHandler handler = configSectionHandlerHandle.Unwrap() as IConfigurationSectionHandler;
        return handler.Create(null, null, doc.DocumentElement);
    }
    return null;
}