APP.Config , Configuration system failed to initialize

[ns]

I am getting the following error
"ConfigurationErrorsException was unhandled, Configuration system failed
to initialize"

This were working fine in Web based application and i am porting it to
windows form, the only thing that i removed is the version ifnormation for
the type in namevalue

I am using Windows Form & .net 2.0

Here is the App.config
===================================================
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<system.diagnostics>
<sources>
<!-- This section defines the logging configuration for
My.Application.Log -->
<source name="DefaultSource" switchName="DefaultSwitch">
<listeners>
<add name="FileLog"/>
<!-- Uncomment the below section to write to the
Application Event Log -->
<!--<add name="EventLog"/>-->
</listeners>
</source>
</sources>
<switches>
<add name="DefaultSwitch" value="Information" />
</switches>
<sharedListeners>
<add name="FileLog"
type="Microsoft.VisualBasic.Logging.FileLogTraceListener,
Microsoft.VisualBasic, Version=8.0.0.0, Culture=neutral,
PublicKeyToken=b03f5f7f11d50a3a, processorArchitecture=MSIL"
initializeData="FileLogWriter"/>
<!-- Uncomment the below section and replace APPLICATION_NAME
with the name of your application to write to the Application Event Log -->
<!--<add name="EventLog"
type="System.Diagnostics.EventLogTraceListener"
initializeData="APPLICATION_NAME"/> -->
</sharedListeners>
</system.diagnostics>

<configSections>
<sectionGroup name="CUSTOMSECTION">
<section name="DEV"
type="System.Configuration.NameValueSectionHandler,System"
restartOnExternalChanges ="false" />
<section name="TEST"
type="System.Configuration.NameValueSectionHandler,System"
restartOnExternalChanges ="false"/>
<section name="PROD"
type="System.Configuration.NameValueSectionHandler,System"
restartOnExternalChanges ="false"/>
</sectionGroup >

</configSections>

<CUSTOMSECTION>
<DEV configSource="DEV.config"/>
<TEST configSource="TEST.config"/>
<PROD configSource="PROD.config"/>

</CUSTOMSECTION>

<appSettings>
<add key ="Environment" value="DEV"/>
</appSettings >
</configuration>

===================================================

here is the DEV.config
===================================================
<DEV>
<add key="SQl_ConString" value="ConnectionString for SQL"/>
<add key="OLEDB_ConString" value="ConnectionString for OLEDB"/>
</DEV>
===================================================


here is the TEST.config
===================================================
<TEST>
<add key="SQl_ConString" value="ConnectionString for SQL"/>
<add key="OLEDB_ConString" value="ConnectionString for OLEDB"/>
</TEST>
===================================================


here is the PROD.config
===================================================
<PROD>
<add key="SQl_ConString" value="ConnectionString for SQL"/>
<add key="OLEDB_ConString" value="ConnectionString for OLEDB"/>
</PROD>
===================================================

 

[ns]

I found the issue.
The configSection should be first xml element after the Root.
Moving it to the top solves the initialization Error.

But now i have another problem, i am not able to load External Files.
It throws an error in the Getsection Line

"Unable to open configSource file 'DEV.config'. (D:\Visual Studio
2008\VAS_AuditLogProcessor\VAS_AuditLogProcessor\bin\Debug\VAS_AuditLogProcessor.vshost.exe.config line 13)"

What would i be doing Wrong

 

[ns]

I was finally able to resolve both the issue.
In the proprty windows for DEV.Config and PROD.Config and TEST.config
i had to mention Copy always.

All the error are resolved now