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

Question

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> 

Answer 1

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> 

Answer 2

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.