.NET 3.5 - Configuration system failed to initialize exception

Question

In my winform app, I am trying to add a userSetting, although the error is occuring with appSettings too. When the setting is added I get an exeption thrown that says: "Configuration system failed to initialize" with a Inner Exception "Unrecognized configuration section userSetting"

Exception Details:

System.Configuration.ConfigurationErrorsException was unhandled
  Message="Configuration system failed to initialize"
  Source="System.Configuration"
  BareMessage="Configuration system failed to initialize"
  Line=0
  StackTrace:
       at System.Configuration.ConfigurationManager.PrepareConfigSystem()
       at System.Configuration.ConfigurationManager.RefreshSection(String sectionName)
       at System.Configuration.ClientSettingsStore.ReadSettings(String sectionName, Boolean isUserScoped)
       at System.Configuration.LocalFileSettingsProvider.GetPropertyValues(SettingsContext context, SettingsPropertyCollection properties)
       at System.Configuration.SettingsBase.GetPropertiesFromProvider(SettingsProvider provider)
       at System.Configuration.SettingsBase.GetPropertyValueByName(String propertyName)
       at System.Configuration.SettingsBase.get_Item(String propertyName)
       at System.Configuration.ApplicationSettingsBase.GetPropertyValue(String propertyName)
       at System.Configuration.ApplicationSettingsBase.get_Item(String propertyName)
       at Settings.get_ApplicationData() in \Properties\Settings.Designer.cs:line 41
       at Common.Initialize.IsSettingsInitialized() 
       at SurveyClient.Program.Main() 
       at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
       at System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)
       at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()
       at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
       at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
       at System.Threading.ThreadHelper.ThreadStart()
  InnerException: System.Configuration.ConfigurationErrorsException
       Message="Unrecognized configuration section userSettings.
       Source="System.Configuration"
       BareMessage="Unrecognized configuration section userSettings."
       Line=3
       StackTrace:
            at System.Configuration.ConfigurationSchemaErrors.ThrowIfErrors(Boolean ignoreLocal)
            at System.Configuration.BaseConfigurationRecord.ThrowIfParseErrors(ConfigurationSchemaErrors schemaErrors)
            at System.Configuration.BaseConfigurationRecord.ThrowIfInitErrors()
            at System.Configuration.ClientConfigurationSystem.OnConfigRemoved(Object sender, InternalConfigEventArgs e)
       InnerException: 

Answer 1

I had some user settings, then removed all of them and started seeing this exception - but only when running the app without debugging. It worked fine when debugging the app. The reason is that user-level settings are "cached" in the Local Application Data folder, and in fact are not read from the MYAPP.exe.config. So what I did was go to C:\Users\MYUSERNAME\AppData\Local\MYCOMPANY\MYAPP.exe_Url_longnastyhash9982749827349879\1.0.0.0\user.config (this is on Win7, the path depends on OS) and removed that folder (with the long hash) altogether. The exception went away. BTW, depending on how your settings are setup this user.config file may be under \AppData\Local or \AppData\Roaming.