There are situations (infrastructure component used across the enterprise is one example) where it is more useful to put the assembly in to the GAC.
Using Heat, a transform needs to be used that will add the assembly=".net" to the wixobj.
In the wixproj File, add a transforms line:
<ItemGroup>
<HeatProject Include="@(ProjectReference->'%(FullPath)')">
<ProjectOutputGroups>Binaries;Symbols;Documents;Satellites;Content</ProjectOutputGroups>
<Transforms>....BuildUtilitiesXSLTHeatGAC.xslt</Transforms>
</HeatProject>
</ItemGroup>
The XSLT file contents:
<?xml version="1.0" encoding="utf-8"?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:msxsl="urn:schemas-microsoft-com:xslt" exclude-result-prefixes="msxsl" xmlns:wix="http://schemas.microsoft.com/wix/2006/wi">
<xsl:output method="xml" indent="yes"/>
<!-- Start the processing from the root copying-->
<xsl:template match="wix:*|@*">
<xsl:copy>
<xsl:apply-templates select="text()|*|@*" />
</xsl:copy>
</xsl:template>
<!-- Search for elements that have a file source, and add an attribute that will let wix GAC them-->
<xsl:template match="*">
<xsl:element name="File" namespace="http://schemas.microsoft.com/wix/2006/wi">
<xsl:attribute name="Id">
<xsl:value-of select="@Id"/>
</xsl:attribute>
<xsl:attribute name ="Source">
<xsl:value-of select="@Source"/>
</xsl:attribute>
<xsl:attribute name="Assembly">.net</xsl:attribute>
<xsl:attribute name="KeyPath">yes</xsl:attribute>
</xsl:element>
</xsl:template>
</xsl:stylesheet>
This will harvest all the output assemblies and flag them to be installed in to the GAC