.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

Try checking that the app.config (myapp.exe.config once deployed) file exists and has at the top (possibly with other bits)

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<configSections>
<sectionGroup name="userSettings"
    type="System.Configuration.UserSettingsGroup, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" >
</sectionGroup>

Answer 2

Probably the problem is that your config file doesn't comply with its schema. For example, this issue can be recreated by duplication the ConnectionStrings section.

Answer 3

I get this error when I write my App.Config (stupidly) as below.

<?xml version="1.0" encoding="utf-8" ?>
<configuration>

<!--List of XMLFiles Begins -->
    <add key="ConfigFileEnvironment" value="C:\Program Files\MyProduct\Config\Environment.xml" />
<!--List of XMLFiles Ends -->

</configuration>

Notice, that there is no appSettings? I used to do this mistake regularly...