An installer I have created with WiX installs a DLL using the SystemFolder
variable, as well as a C# app into another folder. I want to directly reference the DLL from the app. Do I need to look up registry keys to find where the SystemFolder
is?
No, you don't need to query the registry. Windows Installer has a series of built-in properties that automatically resolve to special well known locations such as SystemFolder.
See System Folder Properties for more general information. For WiX, just create a Directory element as a direct child of the TARGETDIR Directory element:
<Directory Id="TARGETDIR" Name="SourceDir">
<Directory Id="SystemFolder" Name="SystemFolder" />
</Directory>
If you already know this and want to know how to reference the DLL from C#, SystemFolder is in the search path so I'm not sure why you'd have to. If it was me, I'd compile the C# as x86 ( AnyCPU is somewhat out of vogue now ) and use:
string myDllPath = Path.Combine( System.Environment.SystemDirectory, "my.dll" );