What is wrong with my app.config file?

Question

I have an app.config file that looks like this:

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <appSettings>
    <add key="TestKey" value="TestValue" />
  </appSettings>
  <newSection>
  </newSection>
</configuration>

And I'm trying to use it in this way:

System.Configuration.ConfigurationFileMap fileMap = new ConfigurationFileMap(@"C:\app.config");  
System.Configuration.Configuration configuration = System.Configuration.ConfigurationManager.OpenMappedMachineConfiguration(fileMap); 

However, it doesn't seem to be working. When I break and debug right after the file is read in, and I try to look at configuration.AppSettings I get an 'configuration.AppSettings' threw an exception of type 'System.InvalidCastException'.

I'm sure I'm reading the file, because when I look at configuration.Sections["newSection"] I am returned an empty {System.Configuration.DefaultSection} (rather than null).

I'm guessing I've got something very basic wrong...what's going on with AppSettings?

Answer 1

You are using a wrong function to read the app.config. OpenMappedMachineConfiguration is intended to open your machine.config file, but you are opening a typical application.exe.config file. The following code will read your app.config and return what you'd expect.

    System.Configuration.ExeConfigurationFileMap fileMap = new ExeConfigurationFileMap();
    fileMap.ExeConfigFilename = @"C:\app.config";
    System.Configuration.Configuration configuration = System.Configuration.ConfigurationManager.OpenMappedExeConfiguration(fileMap, ConfigurationUserLevel.None);
    MessageBox.Show(configuration.AppSettings.Settings["TestKey"].Value);

Answer 2

I think the 'newSection' element is causing the problem. Unless you add a 'configSections' element too, to declare what 'newSection' is, .NET won't be able to cast it.

You need something like:

<configSections>
  <section name="newSection" type="Fully.Qualified.TypeName.NewSection,   
  AssemblyName" />
</configSections>

In the first instance, I'd try removing the 'newSection' element to see if this improves the situation.

This link explains about Custom Configuration Sections.