<PropertyRef Id="NETFRAMEWORK40FULL"/>
<PropertyRef Id="NETFRAMEWORK45"/>

<Condition Message='This setup requires Microsoft .NET Framework 4.0 Full package or greater needs to be installed for this installation to continue.'>
  <![CDATA[Installed OR NETFRAMEWORK40FULL]]>
</Condition>
<Condition Message='This setup requires Microsoft .NET Framework 4.5 package or greater needs to be installed for this installation to continue.'>
  <![CDATA[Installed OR NETFRAMEWORK45]]>
</Condition>

http://wixtoolset.org/documentation/manual/v3/customactions/wixnetfxextension.html

原文：

http://***.com/questions/16302626/how-can-i-check-net-framework-4-5-prerequestics-in-wix