Registry-Free COM Registration
InstallShield 2008
With Reg-Free COM, COM data is written to an application manifest file that is stored in the application folder. The manifest file is an XML file that contains information about an application and the libraries that are associated with it. Note that the Reg-Free COM manifest file, the executable file, and the COM libraries should all be installed to the same folder on the target machine.
Benefits of Reg-Free COM
Reg-Free COM has several advantages over traditional COM. For example, with Reg-Free COM, the component is defined within the scope of the application itself. Even if other applications that use the same COM component or a different version of it require that it be registered, it will not interfere with this application.
Problems may occur with traditional COM registration if multiple versions of shared libraries exist on a target system. For example, an installation may overwrite a new version of a shared library with an older version, or a new version might not be backwardly compatible with older versions. This may cause applications that require features of a specific version to crash. These types of situations are commonly known as DLL Hell. With Reg-Free COM, you can avoid these problems because other applications cannot access your application’s COM component.
In addition, Reg-Free COM streamlines the upgrade and uninstallation processes. For an upgrade, simply replace the application folder. For an uninstallation, simply remove that folder.
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Registry-free COM is a method for deploying COM components such that they do not need to be registered on the target machine. This has two main benefits for OpenViz Particles application deployment:
- Simplified deployment. Applications can now be deployed simply by copying a folder of files to the machine. MSI, batch or manual registering of the COM dlls is not needed.
- Reduced permissions. Because the registry is not touched, applications can be installed by a user without adminstrator or power user permissions. This has long been a problem with COM-based applications, as well as OpenViz Particles .NET applications which depend on the COM dlls.
Registry-free COM may also be referred to by the terms "Isolated Application", "Side-by-Side Assemblies" or "SxS".
Limitations of Reg-Free COM
Reg-Free COM is not appropriate for some solutions. Several limitations exist:
- Reg-Free COM works on only Windows XP or later.
- A component is not suitable for Reg-Free COM if it is a system component or part of the operating system. In addition, it is not suitable if it is a data access component such as Microsoft Data Access Components (MDAC). These types of components should not be isolated. Some of these components, such as MDAC, can be included in an installation as a redistributable.
- A COM component can be isolated only once per application. Consider grouping COM components in a single class library as a workaround to this limitation.