Unable to add customAppSettingsGroup inside my console application app.config - asp.net

Question

I am working on an asp.net console application , and i am trying to add a custom app settings section to encrypt it, as follow:-
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<customAppSettingsGroup>
<customAppSettings>
<add key="KeyOne" value="****" />
</customAppSettings>
</customAppSettingsGroup>
<appSettings>
<add key="ConcurrentRequests" value="100" />
<add key="ApiLimit" value="100" />
<add key="FullScanDay" value="Tuesday" />
<add key="logsFilePath" value="C:\logslogs\" />
<add key="TPSFilePathAndName" value="C:\ctps_ns.txt" />
<add key="PhoneNumberLength" value="11" />
</appSettings>
<startup>
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.6.1" />
</startup>
</configuration>
but when i run the console application i will get this error:-
ConfigurationErrorsException: Unrecognized configuration section customAppSettingsGroup.
any advice?
EDIT-
I tried this inside my app.config:-
<configuration>
<configSections>
<sectionGroup name="customAppSettingsGroup">
<section name="customAppSettings"
type="System.Configuration.NameValueSectionHandler,System" />
</sectionGroup>
</configSections>
<customAppSettingsGroup>
<customAppSettings>
<add key="KeyOne" value="****" />
</customAppSettings>
</customAppSettingsGroup>
<appSettings>
<add key="ConcurrentRequests" value="100" />
<add key="ApiLimit" value="100" />
<add key="FullScanDay" value="Tuesday" />
<add key="logsFilePath" value="C:\logslogs\" />
<add key="TPSFilePathAndName" value="C:\ctps_ns.txt" />
<add key="PhoneNumberLength" value="11" />
</appSettings>
<startup>
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.6.1" />
</startup>
</configuration>
but when i try to access the section using this code:-
NameValueCollection settings = ConfigurationManager.GetSection("customAppSettingsGroup/customAppSettings") as System.Collections.Specialized.NameValueCollection;
i got this exception:-
Could not load file or assembly 'System' or one of its dependencies.
The system cannot find the file specified.'

Answer 1

Try it this way
<configuration>
<configSections>
<sectionGroup name="customAppSettingsGroup">
<section name="customAppSettings"
type="System.Configuration.NameValueSectionHandler,System" />
</sectionGroup>
</configSections>
<customAppSettingsGroup>
<customAppSettings>
<add key="KeyOne" value="****" />
</customAppSettings>
</customAppSettingsGroup>
<appSettings>
<add key="ConcurrentRequests" value="100" />
<add key="ApiLimit" value="100" />
<add key="FullScanDay" value="Tuesday" />
<add key="logsFilePath" value="C:\logslogs\" />
<add key="TPSFilePathAndName" value="C:\ctps_ns.txt" />
<add key="PhoneNumberLength" value="11" />
</appSettings>
<startup>
<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.6.1" />
</startup>
</configuration>