The installer sets this variable to the version of the Fusion.dll file if the installer runs on a system with common language runtime support (i.e., .Net support), for example 2.0.57527.0. If Fusion.dll is not present, this variable is not set.
Note: From .Net version 3.0 onwards, the version number is read from the registry instead of Fusion.dll as a more accurate indicator of the installed runtime version.
You can refer to this variable as <MsiNetAssemblySupport>. In conditional expressions you can omit the brackets and simply use MsiNetAssemblySupport as a test for .Net assembly support. Set automatically by all installers. You can use this version number with runtime functions such as $vercmp to test for specific .Net versions. Alternatively, you can use the VersionCLR variable for a simpler (and less accurate) version check.
You can compare version numbers directly using the standard relational operators < <= > >= = and <>, so a conditional expression like MsiNetAssemblySupport > 3.1 will do a proper version comparison, obviating the need for the $vercmp function.