title: Two projects with the same App.config, one of them doesn't compile
body: <p>I have two windows Form apps with C# and .NET Framework 4.0.</p>
  
  <p>On both projects I have this App.Config:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;configuration&gt;
    &lt;configSections&gt;
      &lt;sectionGroup name="userSettings" type="System.Configuration.UserSettingsGroup, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"&gt;
        &lt;section name="CameraSim.Properties.Settings" type="System.Configuration.ClientSettingsSection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" allowExeDefinition="MachineToLocalUser" requirePermission="false" /&gt;
      &lt;/sectionGroup&gt;
  
      &lt;section name="entityFramework" type="System.Data.Entity.Internal.ConfigFile.EntityFrameworkSection, EntityFramework, Version=6.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" requirePermission="false" /&gt;
    &lt;!-- For more information on Entity Framework configuration, visit http://go.microsoft.com/fwlink/?LinkID=237468 --&gt;&lt;/configSections&gt;
    &lt;startup&gt;
      &lt;supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.0" /&gt;
    &lt;/startup&gt;
    &lt;userSettings&gt;
      &lt;CameraSim.Properties.Settings&gt;
        &lt;setting name="TRZICConn" serializeAs="String"&gt;
          &lt;value&gt;Data Source=UIC181;Initial Catalog=TRZIC-L;Integrated Security=False;User ID=xxxxxxx;Password=xxxxx;Connect Timeout=15;Encrypt=False;TrustServerCertificate=False&lt;/value&gt;
        &lt;/setting&gt;
      &lt;/CameraSim.Properties.Settings&gt;
    &lt;/userSettings&gt;
    &lt;entityFramework&gt;
      &lt;defaultConnectionFactory type="System.Data.Entity.Infrastructure.SqlConnectionFactory, EntityFramework" /&gt;
      &lt;providers&gt;
        &lt;provider invariantName="System.Data.SqlClient" type="System.Data.Entity.SqlServer.SqlProviderServices, EntityFramework.SqlServer" /&gt;
      &lt;/providers&gt;
    &lt;/entityFramework&gt;
    &lt;runtime&gt;
      &lt;assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1"&gt;
        &lt;dependentAssembly&gt;
          &lt;assemblyIdentity name="System.Net.Http" publicKeyToken="b03f5f7f11d50a3a" culture="neutral" /&gt;
          &lt;bindingRedirect oldVersion="0.0.0.0-2.2.29.0" newVersion="2.2.29.0" /&gt;
        &lt;/dependentAssembly&gt;
      &lt;/assemblyBinding&gt;
    &lt;/runtime&gt;
  &lt;/configuration&gt;
  </code></pre>
  
  <p>In one of them the project compiles without any problem, but in the other one don't.</p>
  
  <p>The error is:</p>
  
  <blockquote>
    <p>You can not find schema information for the 'usersettings' element.</p>
  </blockquote>
  
  <p>I have the same error with supportedRuntime, version, sku, setting, etc.</p>
  
  <p>What have I forgotten?</p>
  
  <p>I have also test this <a href="https://msdn.microsoft.com/es-es/library/ms229207%28v=vs.100%29.aspx" rel="nofollow">one</a>, but I'm having the same problems. And on that page doesn't say anything about doing something else like adding a dll.</p>