Wpf.net4 run the machine. Net45?

Working up the files app. config how should be taken?

I am using this code but do not take the solution?

<?xml version="1.0" encoding="utf-8" ?>
<configuration>
  <startup>
    <supportedRuntime version="v4.0"
                      sku=".NETFramework,Version=v4.5" />
  </startup>
  <!--<startup useLegacyV2RuntimeActivationPolicy="true" >    
    <supportedRuntime version="v4.0.30319" sku=".NETFramework,Version=v4.0" />     
  <requiredRuntime version="v4.0.30319" /> 
  </startup>-->
  <!--<system.web>
    <compilation debug="true"
                strict="false"
                explicit="true"
                targetFramework="4.5" />
  </system.web>-->
</configuration>