Only one configSections element allowed per config file and if present must be the first child of the root configuration element

I am developing the console application and when I run the .exe file, I get the following error:

> system.Configuration.ConfigurationErrorsException: Only one <configSections> element allowed per config file and if present must be the first child of the root <configuration> element.

Here's my App.config file:

<configuration>
	<startup useLegacyV2RuntimeActivationPolicy="true">
		<supportedRuntime version="v4.0"/>
	</startup>
	<configSections>
		<section name="Reva.Properties.Settings" type="System.Configuration.ClientSettingsSection, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
		<section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
	</configSections>
    <!-- ... -->

However, if I remove the following startup section, then it works fine

<startup useLegacyV2RuntimeActivationPolicy="true">
    <supportedRuntime version="v4.0"/>
</startup>

The error message itself actually details the correct fix:

> configSections must be the first child* of the root element:

^{*emphasis added}

So just move the configSections to the top:

<configuration>
    <configSections>
        <section name="Reva.Properties.Settings" type="System.Configuration.ClientSettingsSection, System, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" />
        <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
    </configSections>
    <startup useLegacyV2RuntimeActivationPolicy="true">
        <supportedRuntime version="v4.0"/>
    </startup>
</configuration>

The Error web.config File

 <?xml version="1.0" encoding="utf-8"?>   
  
<configuration>    
   <connectionStrings>   
      <add name="SQLConnect" 
           connectionString="Data Source=SAHIL; Initial Catalog=Demo; Integrated Security=SSPI" 
           providerName="System.Data.SqlClient" />   
   </connectionStrings>     
  
   <configSections>   
      <sectionnamesectionname="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, 
          Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" /> 
   </configSections>  
    
   :   
   :   
   :   
   :   
   :   
   :   
   :   
</configuration> 

The Error Was

To fix the error, I rearranged the elements and the error was fixed.